Psych Stats Exam #3

A 95% confidence interval is most commonly used when the alpha level is.... A. .05 B. 0.1 C. .01 D. .001

.05

In a class of 40 students, there are 10 males and 30 females. Half of the class is psychology majors, 2 of whom are males. If a student is elected at random, what is the chance that they are male psychology major? A. .05 B. .1 C. .2 D. .5

.05

A researcher finds the neuroticism and self-reported number of close friends are significantly correlated, r=-.7. What is the effect size for this correlation? A. -.7 B. -.49 C. .49 D. 1.4

.49

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

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

0.05

A set of 30 exam scores with a mean of 60 and a SD of 5 is converted to z-scores. What will be the standard deviation of the transformed scores? A. 0 B. 1 C. 5 D. 60

1

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 there variance of the transformed scores? A. 0 B. 1 C. 5 D. 25

1

The probability of a 95% confidence interval including the SAMPLE MEAN is... A. 0 B. 0.05 C. 0.95 D. 1

1

A population of N=10 scores has mean =50 and a standard deviation =5. What is the population variance? A. square root of 5 B. square root of 50 C. 10 D. 25

25

A population of N=8 scores has EX=40. What is the population mean? A. 320 B. 20 C. 5 D. 0.2

5

What type of scale of measurement doesn't involve measuring a quantity? A. Nominal B. Ordinal C. Interval D. Ratio

Nominal

What kind of distribution shape can Not be symmetrical? A. Unimodal B. Bimodal C. Uniform D. Skewed

Skewed

Which confidence interval would lead one to NOT reject the null hypothesis that the population mean is zero? (Assume that the proprability of type 1 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 95% confidence interval from -2 to 5

A good analogy for type 2 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

a blood test incorrectly indicating that a person does not have lycanthropy

If rejecting the null is thought of a "positive" test result and failing to reject a "negative," a Type 2 error could also be called: A. a false positive B. a false negative C. a true positive D. a true negative

a false negative

All other things being equal, in which scenario, would the p value for the independent samples t-test most likely be less than 0.5? A. a mean difference of 6 points and an n of 60 B. a mean difference of 6 points and an n of 30 C. a mean difference of 3 points and an n of 30 D. a mean of difference of 3 points and an n of 60

a mean difference of 6 points an an of 60

What is the advantage of correlational research designs? A. they often do not require a controlled labratory environment B. they allow you to do research on variables that you cannot or should not manipulate C. they allow you to assess the relationships between variables D. all of the above

all of the above

Variables can be _____, but measurements are always ______ A. continuous, discrete B. continuous, continuous C. measurable, immeasurable D. constant, variable

continuous, discrete

To assess students' interest in class lectures, an instructor tracks daily attendance. "Interest" would be an example of what type of variable? A. continuous, qualitative B. Continuous, quantitative C. discrete, qualitative D. discrete, quantitative

continuous, quantitative

A sample size increases, the standard error of the mean... A. increases B. decreases C. can increase or decrease D. does not change

decreases

What term is used to denote statistics that are only derived from the individuals in the study and not from the larger group of individuals that you, as the researcher, is interested in? A. descriptive statistic B. infernal statistic C. population parameters D. population statistics

descriptive statistic

If rejecting the null is thought of as "positive" test result and failing to reject it a "negative," a type 2 error could also be called a: A. false positive B. false negative C. true positive D. true negative

false negative

What is one way to decrease the standard error of the mean? A. only measure ratio scales B. increase the sample size C. subtract 1 from every score D. measure individual scores instead of sample means

increase the sample size

In a non-normal distribution, the probability of selecting a score that is above two standard deviations from the mean is.... A. .9772 B. .0228 C. .4772 D. It is impossible to tell

it is impossible to tell

Which of these is the correct interpretation of the p value? A. if it large, it means there is statistical signficance B. it shows the probability that you would have obtained the sample statistics value or more extreme if the null were not true C. it shows the probability that you would have obtained the sample statistic's value or more extreme if the null were true D. none of the other options are correct

it shows the probability that you would have obtained the sample statistics's value or more extreme if the null were true

The larger the level of confidence, the ______ precise the interval estimate. A. more B. less C. most D. none of the options are correct

less

If you have a score of X = 75 on an exam, which set of parameters would give you the highest position within the class? A. mean of 70, standard deviation of 5 B. mean of 70, standard deviation of 10 C. mean of 60, standard deviation of 5 D. mean of 60, standard deviation of 10

mean of 60, standard deviation of 5

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

narrow, weaker

A group of heigh scores is shown in a histogram, if the bars in the histogram gradually increase as you go further to the right, this would show.... A. negative distribution B. positive distribution C. Normal Distribution D. Bimodal Distribution

negative distribution

A group of height scores is shown in a histogram. If the bars in the histogram gradually increase as you go further to the right, this would show a.... A. Negative distribution B. positive distribution C. normal distribution D. bimodal distribution

negative distribution

Suppose a class takes a quiz and the majority of scores are high with fewer low scores. Which is the most likely shape of the distribution? A. Negatively Skewed B. Positively Skewed C. Normal D. Symmetrical

negatively skewed

Dr. Stake conducts that students who study more get higher average statistics grades than students who study less, and there are actually is a difference at the population level. What kind of error has she made? A. a type 1 error B. a type 2 error C. a standard error D. no error has been made

no error has been made

The course numbers for 2000-level courses (for example, MATH 2331) are examples of which scale of measurement? A. nominal B. ordinal C. interval D. ratio

nominal

Bar graphs are used to represent the frequency for which type of variables? A. only nominal B. interval and ratio C. only interval D. nominal and ordinal

nominal and ordinal

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

none of the above

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 SD of population 2 D. none of the above

none of the above

Measures of effect 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--now how large the effect is

null hypothesis testing only allows you to conclude whether or not there is a significant effect--now how large the effect is

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

only 10% of the students who took the test scored higher than you

Determining the class standing for the graduating seniors at the high school would involve measurement on a ____scale? A. ordinal B. nominal C. interval D. ratio

ordinal

If the bars on a histogram are highest when scores are lowest and much less frequent for higher scores, the shape of the histogram would be: A. symmetrical B. positively skewed C. negatively skewed D. bimodal

positively skewed

An advantage of the steam and leaf display over a histogram is that it.... A. reduces the number of outliers B. results in a symmetric distribution C. is easier to use when the number of scores is large D. provides the original individual values

provides the original individual values

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. math the participants in two groups on important variables D. ask participants to volunteer for one group or the other

randomly assign participants to two different groups

Which of the following best describes a Type 1 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

rejecting a true 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

retain the null hypothesis

The standard error is used instead of the standard deviation when examining.... A. sample means rather than individual scores B. individual scores rather than sample means C. sample means rather than sample variances D. sample variances rather than sample means

sample means rather than individual scores

In a hypothesis test, the critical region consists of... A. sample values that are highly likely to 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

sample values that are very unlikely to be obtained if the null hypothesis is true

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

the critical region is the same size in both tests

The denominator 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 samples means observed in the study

the difference between the two sample means you can expect to get by chance

The denominator 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 an expect to get by chance D. the difference in the two samples means observed in the study

the difference between the two sample means you can expect to get by chance

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 an expect to get by chance D. the difference in the two sample means observed in the study

the difference in the two samples means observed in the study

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

the estimate will be less precise

All other thing being equal which of the following is true? A. the larger the absolute value of your test statistic, the smaller you 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

the larger the absolute value of your test statistic, the smaller your p value

The higher the confidence interval A. the larger the range of values as estimates of the population B. the smaller 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

the larger the range of values as estimates of the population

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 the 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

the likelihood of rejecting the null increases and there is little to no effect on the effect size

What 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

the mean of a population

Which of the following is an example of a descriptive statistic? A. the estimated mean of a population's IQ B. the predicted rainfall next month C. the expected score on a future test D. the mean of a sample of test scores

the mean of a sample of test scores

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

the mean of the distribution of sample means

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

the mean of the sample (single sample study) or the mean difference in the samples (two-group study)

What would be a reasonable null hypothesis for a two-sample t-test? A. the population mean differs B. the population means are the same C. the sample means differ D. the sample means are the same

the population means are the same

What would be the 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 differe D. the sample means are the same

the population means are the same

If each sample includes only 1 score, the standard error the sample means would be... A. the population mean B. the population standard deviation C. the population variance D. the population median

the population standard deviation

The alpha level determines... A. the probability of a Type 1 error B. the probability of a Type 2 error C. the critical value of the test statistic D. the effect size

the probability of a type 1 error

Which of the following is least likely to be found if a sample is randomly drawn from a population? A. the sample mean is 2.5 standard errors from the population mean B. the sample mean is 1.8 standard errors from the population mean C. the sample mean is 1 standard error from the population mean D. the sample mean is .01 standard errors from the population mean

the sample mean is 2.5 standard errors from the population mean

As the sample size becomes very large... A. the standard error becomes very small B. the standard error becomes very large C. the standard error changes from negative to positive values D. the population variance increases

the standard error becomes very small

The statistical output for an independent samples t-0test shows t(32)=1.26, p=.50. this output indicates that.... A. the study had 33 participants and you should conclude that 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

the study had 34 participants and you should conclude that the two groups are NOT significantly different

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 thee 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

the study had 34 participants and you should conclude that the two groups are NOT significantly different

The mean of the sampling distribution of the mean is always equal to.... A. the true population mean (or your best estimate of it) B. the sample mean C. the sample mean minus 1 D. None given

the true population mean (or your best estimate of it)

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

the two population means are different

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

the two population means are different

A two sample t-test result sin an obtained value for t of zero. When will this happen? A. the two population 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 variancer

the two samples have the same mean

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

the two samples have the same mean

A two-sample t-test results in an obtained value for t of zero. When will this happen? A. the two population 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

the two samples have the same mean

In a histogram or a line graph, what is represented on the x-axis? A. the number of values of a variable B. the values of a variable C. the number of times each variable occurs D. the number of times each value of a variable occurs

the values of a variable

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 population means C. one sample mean is different from the other sample mean D. one population mean is different from the other population mean

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 population means C. one sample mean is different from the other sample mean D. one population mean is different from the other population mean

there is no difference between the two population means

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. there was no significant difference in test scores between those that received the encouraging words and those that did not B. the group that received the encouraging words had significantly higher test scores than the control group C. there was a significant difference in test scores between the groups D. none of the above

there was a significant difference in test scores between the groups

Which of the following describes why confidence intervals are often useful? A. they tell us the standard deviation fo the population B. they change the probability of receiving a significant result C. they decrease the power of the designs D. they provide a range of estimated values for the population mean rather than a single number

they provide a range of estimated values for the population mean rather than a single number

Dr. Stake concludes that morning statistics classes don't differ from afternoon classes in average grade. However, there actually is difference at the population level. What kind of error has she made? A. a type 2 error B. a type 1 error C. a standard error D. no error has been made

type 2 error

In which of the following scenarios would the assumption of homogeneity of variance be violated. A. when one group has a significantly 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

when one group has a narrow distribution of scores and the other group has a very wide distribution of scores

When is a bar graph more appropriate to use than a histogram? A. when scores are interval scaled B. when scores are discrete C. when scores are a ratio scale D. when scores are continuous

when scores are discrete

The interquartile range for a set of scores tells you.... A. where the middle 50% of the scores lie around the median B. where the middle 90% of the scores lie around the median C. where the top 50% of scores are D. the difference between the highest score in the distribution and the lowest score in the distribution

where the middle 50% of the scores lie around the median

If the value of zero does NOT fall within your confidence interval for a two sample test, A. you are fairly confident that there is no significant difference between your means B. you are fairly confident that there is a significant difference between you means C. the variability of the scores in the sample was quite high D. more information is needed to interpret such a situation

you are fairly confident that there is a significant difference between your means

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 month

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 month