Stat Exam 3
A set of 30 exam scores with a mean of 60 and a standard deviation of 5 is converted to z-scores. What will be the mean of the transformed scores? A) 0 B) 1 C) 5 D) 60
A) 0
A statistics exam has an average score of 75, with a standard deviation of 4. If a student scores an 83 on the exam, what is their z score? A) 2 B) 4 C) 75 D) 83
A) 2
A good analogy for a type I error is... A) A blood test incorrectly indicating that a person has Lycanthropy B) A blood test incorrectly indicating that a person does not have Lycanthropy C) A&B are correct D) None of the above are correct
A) A blood test incorrectly indicating that a person has Lycanthropy
If rejecting the null is thought of as a "positive" test result and failing to reject it a "negative", a Type I error could also be called A) A false positive B) A false negative C) A true positive D) A true negative
A) A false positive
All other things being equal, in which scenario, would the p value for the independent-samples t-test most likely be less than .05? A) A mean difference of 6 points and an n (sample size) of 60 B) A mean difference of 6 points and an n (sample size) of 30 C) A mean difference of 3 points and an n (sample size) of 30 D) A mean difference of 3 points and an n (sample size) of 60
A) A mean difference of 6 points and an n (sample size) of 60
Which statement is true? A) As sample size increases, power increases. B) As sample size decreases, power increases. C) As sample size increases, effect size increases D) As sample size decreases, effect size increases.
A) As sample size increases, power increases.
Which of these is the correct interpretation of the p value? A) It shows the probability that you would have obtained the sample statistic's value or more extreme if the null were true B) It shows the probability that you would have obtained the sample statistic's value or more extreme if the null were not true C) If it is large, it means there is statistical significance D) None of the other options are correct.
A) It shows the probability that you would have obtained the sample statistic's value or more extreme if the null were true
Which of the following sample means will have the largest standard error (sampling error)? A) One where the sample size is 100 and the population standard deviation is 10 B) One where the sample size is 200 and the population standard deviation is 5 C) One where the sample size is 200 and the population standard deviation is 10 D) It is impossible to tell.
A) One where the sample size is 100 and the population standard deviation is 10
A group of researchers believed people's perceived economic status (high or low) would cause changes in their support for political policies that redistributed income. What was their independent variable? A) Perceived economic status B) Changes in support C) Political policies D) Redistribution of income
A) Perceived economic status
The average height for women in the US is about 5 ft 4 in. A woman who is 6 ft tall would have a z-score for height that is A) Positive B) Negative C) 0 D) It is impossible to tell without the standard deviation
A) Positive
All other things being equal (e.g., sample size, etc), which of the following is true? A) The larger the absolute value of your test statistic, the smaller your p value. B) The larger the absolute value of your test statistic, the larger your p value. C) There is no relationship between the test statistic and the p value. D) None of the other options are correct.
A) The larger the absolute value of your test statistic, the smaller your p value.
What information can measures of effect size give us that hypothesis testing alone does not? A) The magnitude of the difference between populations B) The probability there's a difference between populations C) The true means for each population D) The true standard deviations for each population
A) The magnitude of the difference between populations
If all the possible random samples of size = 30 are selected from a population of scores that is positively skewed with a µ = 80 and a δ = 10 and the mean is computed for each sample, then what shape is expected for the distribution of sample means? A) The sample means will form a normal distribution because the sample sizes are relatively large. B) The sample means will be positively skewed because the parent population is positively skewed. C) The sample will be evenly distributed across the scale and form a rectangle shape. D) None of the other options are correct
A) The sample means will form a normal distribution because the sample sizes are relatively large.
A histogram would be used instead of a bar graph if A) The variable is continuous B) The variable is discrete C) The distribution is skewed D) The distribution is symmetrical
A) The variable is continuous
Dr. Vation tests 50 students' short-term memory. He finds one student has a Z-score of -1.5. What does this tell him about the student's memory? A) Their memory score is 1.5 standard deviations below the mean memory score B) Their memory score is 1.5 standard deviations above the mean memory score C) Their memory score is 1.5 memory units below the standard deviation D) Their memory score is 1.5 memory units above the standard deviation
A) Their memory score is 1.5 standard deviations below the mean memory score
When is the mode the only measure of central tendency that can be used? A) When the variable is nominal or categorical B) When the variable is discrete. C) When the distribution is positively skewed D) All of the above.
A) When the variable is nominal or categorical
Which confidence interval would lead one to NOT reject the null hypothesis that the population mean is zero? (Assume that the probability of a Type I error is set at 5%). A) a 95% confidence interval from -2 to 5 B) a 99% confidence interval from 2 to 5 C) a 99% confidence interval from 2 to 5 D) a 5% confidence interval from 2 to 50
A) a 95% confidence interval from -2 to 5
The frequencies of ordinal and norminal variables are best represented by... A) bar graph B) histogram C) frequency polygon (line graph) D) either a histogram or frequency polygon
A) bar graph
You decide to collect information from 500 participants on their level of education obtained (no high school diploma, high school diploma, Associate's Degree, Bachelor's, etc). Which type of graph would be best to use in this scenario? A) bar graph B) histogram C) frequency polygon (line graph) D) either a histogram or frequency polygon
A) bar graph
The owners of Cupid's Stupid Divorce Attorneys discover that they have won 0% of all their client's cases. This is an example of a A) descriptive statistic B) inferential statistic C) both descriptive and inferential statistics D) neither descriptive nor inferential statistics
A) descriptive statistic
A doctor studies a very rare disease with only five known cases. The doctor wants to know the average age of onset of the disease and becasue he is the doctor for all five cases, he can simply look at their medical records. This doctor would likely perform. A) descriptive statistics only B) inferential statistics only C) both descriptive and inferential statistics D) None of the other options are correct
A) descriptive statistics only
The term "inferential" in inferential statistics is appropriate because we A) infer about the characteristics of a population based only on a sample B) infer about the characteristics of a sample based only on a population C) infer about the type of research design that we used D) infer about the expertise of the researcher
A) infer about the characteristics of a population based only on a sample
To get a more precise estimate of a population parameter from a confidence interval, you would need a _________ interval, providing _________ confidence. A) narrow, weaker B) narrow, stronger C) wider, weaker D) wider, stronger
A) narrow, weaker
The course numbers for 2000-level courses (for example, MATH 2331, PSYC 2330, or PSYC 2370) are examples of which scale of measurement? A) nominal B) ordinal C) interval D) ratio
A) nominal
Conceptually, the standard error of the mean tells you A) on average, how far off your samples means are likely to be from the true population mean B) on average, how far off your scores are likely to be from the sample mean C) on average, how far off your scores are likely to be from the population mean D) that the expected value of the sample mean is equal to the population mean
A) on average, how far off your samples means are likely to be from the true population mean
If you scored at the 90th percentile on a test, you would know that A) only 10% of the students who took the test scored higher than you B) you got 90 out of 100 questions correct on the test C) only 10% of the students scored lower than you D) the majority of students scored higher than you
A) only 10% of the students who took the test scored higher than you
The power of a statistical test is best described as the A) probability of finding a significant effect/relationship when one in fact exists in the population B) the probability of finding a Type I error assuming that it exists in the population C) the probability of finding a Type II error assuming that it exists in the population D) the probability of missing a real effect assuming that it exists in the population
A) probability of finding a significant effect/relationship when one in fact exists in the population
The most powerful way to create the groups for an independent samples t-test is to A) randomly assign participants to two different groups B) repeatedly test the same group of participants twice C) match the participants in two groups on important variables D) ask participants to volunteer for one group or the other
A) randomly assign participants to two different groups
If the null hypothesis is outside the confidence interval, then the decision was likely to ______ using hypothesis testing A) reject the null hypothesis B) retain the null hypothesis C) further examine the null hypothesis D) there is not enough information to answer this question.
A) reject the null hypothesis
If the z score for your treated sample mean is NOT in the critical region, then the most appropriate statistical decision is to A) retain the null hypothesis B) reject the null hypothesis C) retain the alternative hypothesis D) reject the alternative hypothesis
A) retain the null hypothesis
A number that describes how likely your sample mean will be close to the true population mean is the A) standard error of the mean B) variance of scores C) standard deviation of scores D) interquartile range
A) standard error of the mean
A standard deviation is conceptually most similar to what? A) the average of all deviations from the mean B) the square of the variance C) the square root of the standard error of the mean D) the highest score minus the lowest score
A) the average of all deviations from the mean
A therapist is investigating the impact of a new treatment for depression compared to an old treatment. Which of the following accurately represents the ALTERNATIVE hypothesis. A) the new treatment produces different results than the old one. B) the new treatment produces results that are the similar to the old treatment C) The new treatment produces better results than the old treatment D) None of the other options are correct.
A) the new treatment produces different results than the old one.
The alpha level determines A) the probability of a Type I error B) the probability of a Type II error C) the critical value of the test statistic D) the effect size
A) the probability of a Type I error
A researcher shows that a new treatment significantly reduces depression, with an r-squared of .25. What is the correct interpretation of this value? A) the treatment accounted for 25% of the variance in depression B) 25% of people benefitted from the treatment C) There was a 25% chance of getting this r value D) none of the other options are correct
A) the treatment accounted for 25% of the variance in depression
When the null hypothesis is rejected in an independent samples t-test, what conclusion is being drawn? A) the two populations being compared probably have different means B) you've proven your hypothesis correct C) the two populations probably do not have different means D) none of the above
A) the two populations being compared probably have different means
Which of the following could be a null hypothesis of a two-tailed hypothesis test? A) the two populations have the same mean B) the two populations have different means C) Population 1's mean is greater than or equal to Population 2's mean D) Population 1's mean is less than Population 2's mean
A) the two populations have the same mean
You just completed a study in which you concluded no significant difference in introversion personality scores between greek and non-greek students. It is possible that A) you are making a Type II error B) you are making a Type I error C) You are making both a Type I and a Type II error D) none of the above are possible
A) you are making a Type II error
R-squared as a measure of effect size will always have a value in the range _________ and indicates the ________. A) 0-100; proportion of variance accounted for B) 0-1; proportion of variance accounted for C) 0-100; size of effect in standard deviations D) 0-1; size of effect in standard deviations
B) 0-1; proportion of variance accounted for
A 95% confidence interval is most commonly used when the alpha level is ________ A) 0.1 B) 0.05 C) 0.01 D) 0.001
B) 0.05
There are 4 aces in a standard deck of 52 cards. What is the probability of drawing 2 aces in a row with replacement (the first card drawn goes back in the deck before the second draw)? A) 0.045 B) 0.059 C) 0.077 D) 0.15
B) 0.059
A sample of 16 scores provides a mean of 12 and a standard deviation of 8. If the null hypothesis states that the population mean is 10, what is the value of Cohen's d? A) 0.125 B) 0.25 C) 0.5 D) 1
B) 0.25
If the variance of a dataset is 16, what is the standard deviation? A) 2 B) 4 C) 16 D) 256
B) 4
Which of the following statements CANNOT be true for a distribution of scores? A) 60% of the scores are above the mean. B) 60% of the scores are above the median. C) 60% of the scores are above the mode. D) All of the above are false statements.
B) 60% of the scores are above the median.
Dr. Stake concludes that morning statistics classes don't differ from afternoon classes in average grade. However, there actually is a difference at the population level. What kind of error has she made? A) A type I error B) A Type II error C) A standard error D) No error has been made
B) A Type II error
A good analogy for a type II error is... A) A blood test incorrectly indicating that a person has Lycanthropy B) A blood test incorrectly indicating that a person does not have Lycanthropy C) A&B are correct D) None of the above are correct
B) A blood test incorrectly indicating that a person does not have Lycanthropy
What disadvantage does a lab study have compared to a field study? A) The researcher can't control the situation as well B) Behavior may be less realistic C) Lab studies cannot show causality. D) Lab studies cannot be replicated
B) Behavior may be less realistic
What is the most common way to create a misleading graph? A) Change the range of scale units on the x-axis B) Change the range of scale units on the y-axis. C) Use a bar graph instead of a histogram. D) Use a histogram instead of a bar graph.
B) Change the range of scale units on the y-axis.
A researcher reports that the size of an effect in Population A is d = 0.10 and the effect size in Population B is d = 0.34. Which population is associated with greater power to detect an effect? A) Population A B) Population B C) The effects are equal in the two populations D) There is not enough information to determine
B) Population B
A researcher increases his level of confidence from 90% to 95%. What will happen to the precision of his estimate? A) The estimate will be more precise B) The estimate will be less precise C) The precision of his estimate will not change. D) It depends on the size of the population
B) The estimate will be less precise
The expected value of the sample mean is A) The obtained sample mean. B) The mean of the distribution of sample means. C) The sample standard deviation. D) The standard deviation of the distribution of sample means.
B) The mean of the distribution of sample means.
What would be a reasonable null hypothesis for a two-sample t-test? A) The population means differ. B) The population means are the same. C) The sample means differ. D) The sample means are the same.
B) The population means are the same.
A new instructional method is found to increase average exam grades from 80.20 to 80.21. That's not much of a change, but it was found to be statistically significant. How could that happen. A) The sample size was very small. B) The sample size was very large. C) The population size was very small. D) The population size was vary large.
B) The sample size was very large.
If the same data is displayed in a frequency polygon (line graph) and a bar graph, how will the shapes of the two graphs differ? A) The bar graph will be more skewed B) There will be no difference in shape C) The frequency polygon will have a higher peak D) The bar graph will have a smaller range
B) There will be no difference in shape
In which of the following scenarios would the assumption of homogeneity of variance be violated. A) When one group has a signicantly higher mean than the other group. B) When one group has a narrow distribution of scores and the other group has a very wide distribution of scores. C) When both groups have scores that have a similar spread. D) When one group has many scores and another group only has a few scores.
B) When one group has a narrow distribution of scores and the other group has a very wide distribution of scores.
Other things held constant, as you increase sample size, the shape of the sampling distribution of the mean will A) increase B) decrease C) could increase or decrease D) not be affected
B) decrease
As sample size increases, the standard error of the mean A) increases B) decreases* C) can increase or decrease D) does not change
B) decreases
Most often, when you arrive at a conclusion about your study's hypothesis, the last step in the statistical analysis requires A) descriptive statistics B) inferential statistics C) graphing the data D) collecting the data
B) inferential statistics
The larger the level of confidence, the ______ precise the interval estimate. A) more B) less C) most D) none of the options are correct
B) less
The variability of the sample means in a sampling distribution will always be A) greater than the variability of scores in the population B) less than the variability of scores in the population C) greater than population standard deviation D) greater than the sample standard deviation
B) less than the variability of scores in the population
Based on the effect size conventions, d = 0.60 is a A) small effect size B) medium effect size C) large effect size D) Not enough information to answer this question
B) medium effect size
It is impossible for a man to give birth. Therefore, sex and ability to give birth are A) independent B) mutually exclusive C) mutually exhaustive D) unrelated
B) mutually exclusive
Determining the class standing (1st, 2nd, and so on) for the graduating seniors at a high school would involve measurement on a(n) _____ scale of measurement.? A) nominal B) ordinal C) interval D) ratio
B) ordinal
The standard error is used instead of the standard deviation when examining A) individual scores rather than sample means B) sample means rather than individual scores C) sample means rather than sample variances D) sample variances rather than sample means
B) sample means rather than individual scores
In a hypothesis test, the critical region consists of A) sample values that are highly likely to be obtained if the null hypothesis is true B) sample values that are very unlikely to be obtained if the null hypothesis is true C) sample values that provide proof that the null hypothesis is true D) sample values that provide proof that the null hypothesis is false
B) sample values that are very unlikely to be obtained if the null hypothesis is true
Which of the following is most similar to a histogram? A) pie chart B) stem-and-leaf display C) normal distribution D) cumulative frequency display
B) stem-and-leaf display
The higher the confidence interval (e.g., 95% vs 90%) A) the smaller the range of values as estimates of the population B) the larger the range of values as estimates of the population C) the smaller the range of values as estimates of the sample D) the larger the range of values as estimates of the sample
B) the larger the range of values as estimates of the population
What is are confidence intervals most often used to estimate? A) the mean of a sample B) the mean of a population C) both the mean of a sample and a population D) neither the mean of a sample nor a population
B) the mean of a population
The midpoint of a confidence interval is always A) the mean of the population (single sample study) or the mean difference in the population (two-group study) B) the mean of the sample (single sample study) or the mean difference in the samples (two-group study) C) the value of zero D) 0.5
B) the mean of the sample (single sample study) or the mean difference in the samples (two-group study)
A therapist is investigating the impact of a new treatment for depression compared to an old treatment. Which of the following accurately represents the NULL hypothesis A) the new treatment produces different results than the old one. B) the new treatment produces results that are the similar to the old treatment C) The new treatment produces better results than the old treatment D) None of the other options are correct.
B) the new treatment produces results that are the similar to the old treatment
If each sample includes only 1 score, the standard error of the sample means would be A) the population mean B) the population standard deviation C) the population variance D) the population median
B) the population standard deviation
All other things being equal, the larger your sample size (n)... A) the larger the standard error of the mean B) the smaller the standard error of the mean C) sample size has no impact on the standard error of the mean D) None of the other options are correct
B) the smaller the standard error of the mean
The null hypothesis for a one-sample test states A) there is no difference between the sample mean and the population mean B) there is no difference between the two population means C) there is a difference between the sample mean and the population mean D) None of the other 3 choices is correct.
B) there is no difference between the two population means
For an independent samples t-test, the null hypothesis states that A) there is no difference between the two sample means B) there is no difference between the two poulation means C) one sample mean is different from the other sample mean D) one population mean is different from the other population mean
B) there is no difference between the two poulation means
You just completed a study in which you concluded that female students had significantly higher GPAs than male students. It is possible that A) you are making a Type II error B) you are making a Type I error C) You are making both a Type I and a Type II error D) none of the above are possible
B) you are making a Type I error
A researcher finds that neuroticism and self-reported number of close friends are significantly correlated, r = -.7. What is the effect size for this correlation? A) -0.7 B) -0.49 C) 0.49 D) 1.4
C) 0.49
A treatment is administered to a sample selected from a population with a mean of = 80 and a standard deviation of = 10. After treatment, the sample mean is M = 85. Based on this information, the effect size as measured by Cohen's d is A) 5 B) 2 C) 0.5 D) not enough information to determine Cohen's d
C) 0.5
A population of N = 8 scores has EX = 40. What is the population mean? A) 320 B) 20 C) 5 D) 0.2
C) 5
A researcher selects two samples of 25 participants each. In the first sample the population mean was 32 and the variance was 8. In this second sample, the population mean was 4 and the variance was 8. Which sample will be associated with a larger standard error of the mean? A) Sample 1 B) Sample 2 C) None, both samples will have the same value for standard error D) There is not enough information to answer this question
C) None, both samples will have the same value for standard error *They have the same variance
Which of the following best describes a Type I error? A) Failing to reject a true null hypothesis B) Failing to reject a false null hypothesis C) Rejecting a true null hypothesis D) Rejecting a false null hypothesis
C) Rejecting a true null hypothesis
Which of the following is true when you increase the sample size for a study? A) The likelihood of rejecting the null and the effect size both increase B) The likelihood of rejecting the null and effect size both decrease C) The likelihood of rejecting the null increases and there is little to no effect on the effect size D) The likelihood of rejecting the null decreases and there is little to no effect on the effect size
C) The likelihood of rejecting the null increases and there is little to no effect on the effect size
The height of each bar on a frequency histogram represents A) The total number of scores in the sample B) The total number of participants in the sample C) The total number of participants who scored that particular score D) The total number of scores for that particular participant
C) The total number of participants who scored that particular score
A researcher conducts a study in which one group of students receives encouraging words before a test and a control group receives no encouraging words. She examines the impact of this on test scores. The results are as follows: t(40) = 3.00, p = .004. What is the most appropriate conclusion given an alpha level of .05? A) The group that received the encouraging words had significantly higher test scores than the control group. B) There was no significant difference in test scores between those that received the encouraging words and those that did not. C) There was a significant difference in test scores between the groups. D) None of the other options are correct.
C) There was a significant difference in test scores between the groups.
A hypothesis test is A) a descriptive technique that allows researchers to describe a sample B) a descriptive technique that allows researchers to describe a population C) an inferential technique that uses the data from a sample to draw inferences about a population D) an inferential technique that uses information about a population to make predictions about a sample
C) an inferential technique that uses the data from a sample to draw inferences about a population
If a researcher wants to use data from a sample to draw conclusions about a population, they would need to use A) only descriptive statistics B) only inferential statistics C) both descriptive and inferential statistics D) neither descriptive nor inferential statistics
C) both descriptive and inferential statistics
The distance an individual score is from the mean is called... A) the standard deviation B) the variance C) deviation D) sum of squares
C) deviation
A Type II error means that a researcher has A) falsely concluded that a treatment has an effect B) correctly concluded that a treatment has no effect C) falsely concluded that a treatment has no effect D) correctly concluded that a treatment has an effect
C) falsely concluded that a treatment has no effect
A list of all possible values of a variable and the number of times each value occurs is called a A) probability distribution B) measurement C) frequency distribution D) histogram
C) frequency distribution
The standard error of the mean (SE) is like the A) standard deviation for the sample B) standard deviation for the population C) standard deviation for the sampling distribution of means D) None of the other options are correct
C) standard deviation for the sampling distribution of means
Which of the following is NOT a measure of effect size? A) Cohen's d B) r2 (r-squared) C) t score D) None of the above - A, B, and C are all measures of effect size
C) t score
If a researcher conducts both a one-tailed and two-tailed hypothesis test, both with an alpha of .05, which is true of the two tests' critical regions? A) the one-tailed test's critical region is bigger B) the two-tailed test's critical region is bigger C) the critical region is the same size in both tests D) the size of the critical region can't be determined in either test
C) the critical region is the same size in both tests
A predicted effect is tested by a null significance hypothesis test, and a statistically significant result is found. Which of the following describes the most appropriate conclusion to take from the test: A) the effect is proven to exist in the population B) the effect is proven to not exist in the population C) the effect is likely but not certain to exist in the population D) the effect is likely but not certain to not exist in the population
C) the effect is likely but not certain to exist in the population
Cohen's d measures effect size in what units? A) whatever units were used for the variable being considered (e.g., inches, pounds, percent correct) B) the value of the mean of the variable C) the standard deviation of the variable D) the standard error of the mean of the variable
C) the standard deviation of the variable
What would be a reasonable alternative hypothesis for a two-sample t-test? A) the two population means are the same B) the two sample means are the same C) the two population means are different D) the two sample means are different
C) the two population means are different
A two-sample t-test results in an obtained value for t of zero. When will this happen? A) the two populations have the same mean B) the two populations have the same variance C) the two samples have the same mean D) the two samples have the same variance
C) the two samples have the same mean
When we use inferential statistics to arrive at a conclusion in our study A) we have proven the result B) we are sure that others will find the same result when they attempt to replicate our study C) we are confident of our conclusion but realize that we are not 100% sure D) we are 100% sure that our conclusion is true
C) we are confident of our conclusion but realize that we are not 100% sure
If the t-value for your independent samples t-test has a p (probability) value less than your alpha level, then A) you should retain the null hypothesis and conclude that the two group means are NOT significantly different B) you should reject the null hypothesis and conclude that the two group means are NOT significantly different C) you should reject the null hypothesis and conclude that the two group means are significantly different D) you should retain the null hypothesis and conclude that the two group means are significantly different
C) you should reject the null hypothesis and conclude that the two group means are significantly different
The probability of a 95% confidence interval including the SAMPLE MEAN is A) 0 B) 0.05 C) 0.95 D) 1
D) 1
A researcher concludes that a new treatment works significantly better than an existing treatment for improving depression. However, this finding is just unique to the specific sample and does not reflect what would happen in the population. This is an example of... A) A type I error B) incorrectly rejecting the null C) A type 2 error D) A&B are correct
D) A&B are correct
An instructor examines the scores on her first exam, which has a typical scale of 1 to 100 and a fairly normal distribution. Which measure of central tendency is appropriate for this variable. A) The mode B) The median C) The mean D) All of the above
D) All of the above
A researcher reports that the size of an effect in some population is d = 0.88. Which of the following is an appropriate interpretation for d? A) The effect observed in the population was significant. B) Mean scores were significant by 0.88 points in the sample. C) Mean scores were significant by 0.88 points in the population. D) Mean scores shifted 0.88 standard deviations in the population.
D) Mean scores shifted 0.88 standard deviations in the population.
Dr. Stake concludes that students who study more get higher average statistics grades than students who study less, and there actually is a difference at the population level. What kind of error has she made? A) A type I error B) A Type II error C) A standard error D) No error has been made
D) No error has been made
What kind of distribution shape can NOT be symmetrical? A) Unimodal B) Bimodal C) Uniform D) Skewed
D) Skewed
The numerator of an independent-samples t-test represents which of the following? A) The difference between the two sample standard deviations. B) The standard error of the mean. C) The difference between the two sample means you can expect to get by chance. D) The difference in the two sample means observed in the study.
D) The difference in the two sample means observed in the study.
Which of the following studies would best be analyzed with an independent samples t-test? A) You select a group of children diagnosed with ADHD and assess their academic success in class, first with one treatment for a month, then with a second treatment for a month, and then with a third treatment for a month. B) You randomly assign children with a diagnosis of ADHD to three different treatment groups and then compare the three groups on their academic success in class for one month. C) You select a group of children diagnosed with ADHD and assess their academic success in class, first with one treatment for a month and then again with a second treatment for a month. D) You randomly assign children with a diagnosis of ADHD to two different treatment groups and then compare the two groups on their academic success in class for the a month.
D) You randomly assign children with a diagnosis of ADHD to two different treatment groups and then compare the two groups on their academic success in class for the a month.
An independent samples t-test is appropriate for what type of research design? A) a correlational design B) a descriptive design C) a within-participants design D) a between-participants design
D) a between-participants design
A z-score for an x score tells you A) how many standard deviations the score is above or below the mean B) whether the x score is above or below the mean C) a standardized score that is not dependent on the particular values for the variable measured D) all of the above
D) all of the above
Increasing the alpha level (for example from = .01 to = .05) A) increases the size of the critical region B) increases the probability of a Type I error C) increases the probability that the sample will fall into the critical region D) all of the above are true
D) all of the above are true
Confidence intervals are most often used as A) a descriptive statistic to supplement the calculation of the range B) a descriptive statistic to describe the likelihood of making a Type I or Type II error C) an inferential statistic to supplement calculation of correlation coefficients D) an inferential statistic to supplement null hypothesis testing
D) an inferential statistic to supplement null hypothesis testing
You decide to create a graph with mean GPA on the y-axis and number of hours studied per week on the x-axis. Which of the following would be the most appropriate graph to use? A) bar graph B) histogram C) frequency polygon (line graph) D) either a histogram or frequency polygon
D) either a histogram or frequency polygon
Hypothesis testing is a(n) A) descriptive method for determining the scale of measurement used B) descriptive method for estimating variability C) inferential method for determining whether a sample statistic has a particular value D) inferential method for determining whether a population parameter has a particular value
D) inferential method for determining whether a population parameter has a particular value
What population parameters must be known to run an independent samples t-test? A) the mean of Population 1 B) the mean of Population 2 C) the mean and standard deviation of Population 2 D) none of the above
D) none of the above
Measures of effet size are important statistics because A) they are greatly influenced by the sample size B) they are not influenced by the variability of scores in the sample(s) C) easy to calculate D) null hypothesis testing only allows you to conclude whether or not there is a significant effect - not how large the effect is
D) null hypothesis testing only allows you to conclude whether or not there is a significant effect - not how large the effect is
An example of a variable measured on a nominal scale is A) average score on a depression scale B) number of aggressive behaviors C) birth position in a family D) number on an athletic jersey
D) number on an athletic jersey
The number of pets a person has represents which scale of measurement? A) nominal B) ordinal C) interval D) ratio
D) ratio
The best measure of sampling error is the A) sample variance B) sample standard deviation C) population standard deviation D) standard error of the mean
D) standard error of the mean
The measure of variability on a sampling distribution of the mean is the A) population variance B) sample variance C) sample standard deviation D) standard error of the mean
D) standard error of the mean
The correct interpretation of a 95% confidence interval is that A) the sample mean has a 95% chance of being in the interval B) the population mean has a 95% chance of being in the interval C) the interval has a 95% chance of including the sample mean D) the interval has a 95% chance of including the population mean
D) the interval has a 95% chance of including the population mean
A sample of n = 25 individuals is selected from a population with mean = 80 and a treatment is administered to the sample. If the treatment has no effect, then A) the sample mean should be very different from 80 and should lead you to reject the null hypothesis B) the sample mean should be very different from 80 and should lead you to fail to reject (retain) the null hypothesis C) the sample mean should be close to 80 and should lead you to reject the null hypothesis D) the sample mean should be close 80 and should lead you to fail to reject (retain) the null hypothesis
D) the sample mean should be close 80 and should lead you to fail to reject (retain) the null hypothesis
Which of the following defines the expected difference between a population's mean and the mean of a sample randomly drawn from it? A) the population mean B) the population variance C) the standard deviation D) the standard error of the mean
D) the standard error of the mean
The statistical output for an independent samples t-test shows t(32) = 1.26, p = .50. This output indicates that A) the study had 33 participants and you should conclude that the two groups are significantly different B) the study had 33 participants and you should conclude that the two groups are NOT significantly different C) the study had 34 participants and you should conclude that the two groups are significantly different D) the study had 34 participants and you should conclude that the two groups are NOT significantly different
D) the study had 34 participants and you should conclude that the two groups are NOT significantly different
Which of the following describes why confidence intervals are often useful? A) they tell us the standard deviation of the population B) they change the probability of receiving a significant result C) they decrease the power of the design D) they provide a range of estimated values for the population mean rather than a single number
D) they provide a range of estimated values for the population mean rather than a single number
What is one way to decrease the standard error of the mean?
increase the sample size
On a particularly easy general psychology exam, most students got As and nearly everyone else got Bs. There were, of course, a few Cs and even fewer Ds and Fs. The shape of the distribution of scores could be described as
negatively skewed