Psych stats final

For a perfectly symmetrical distribution with a mean of 40, what is the value of the median? A. 40 B. >40 C. <40 D. cannot be determined

A

For any distribution, what is the z-score corresponding to the mean? A. 0 B. 1 C. N D. cannot be determined

A

For the following frequency distribution, what is the proportion associated with X=3? X f 5 2 4 4 3 1 2 3 A. .10 B. .20 C. .30 D. .40

A

What z-score value separates the top 10% of a normal distribution from the bottom 90%? A. z= 1.28 B. z= 0.25 C. z= -1.28 D. z= -0.25

A

a sample has a mean of 72. if one person's score of X=58 is removed from the sample, what effect will it have on a sample mean? A. the sample mean will increase B. the sample mean will decrease C. the sample mean will remain the same D. cannot be determined

A

an analysis of variance produces SStotal=40 and SSwithin=10. For this analysis, what is SSb/w? A. 30 B. 50 C. 400 D. cannot be determined without additional info

A

for a population with μ=100 and σ=20, what is the X value corresponding to z= -0.75? A. 85 B. 95 C. 105 D. 115

A

for an ANOVA comparing 3 treatment conditions, what is stated by the null hypothesis (H0)? A. there are no differences b/w any of the population means B. at least one of the 3 population means is diff. from another mean C. all 3 of the population means are diff. from each other D. none of the other choices are correct

A

for an independent measures ANOVA comparing 3 treatments with a sample of n=5 in each treatment, what is the critical vaue for the F ratio using a=.05? A. 3.88 B. 3.49 C. 3.74 D. 3.34

A

for the past 20 years, the high temp. on april 15th has averaged μ=62 degrees with a SD of σ=12. Last year the high temp. was 68 degrees. Based on this info, which of the following best describes last years temp. on april 15th? A. a little above average B. far above average C. above average, but it is impossible to describe how much above average D. there is not enough info to compare last year with the average

A

on an exam with a population mean of 70, you have a score of 75. Which of the following values for the SD would give you the highest position in the class? A. 1 B. 5 C. 10 D. cannot be determined

A

on average, what value is expected for the t stat when the null hypothesis is true? A. 0 B. 1 C. 1.96 D. t>1.96

A

the data from an independent measures study produce a sample mean diff. of 6pts and an estimated standard error of 2pts. If there are n=8 scores in each sample, then the value for the t stat is______ A. 6/2 B. 6/4 C. 6/0.25 D. 6/0.50

A

the value of one score in a distribution is changed from X=20 to X=30. which measure(s) of central tendency is/are certain to be changed? A. the mean B. the median C. the mean and median D. the mode

A

what symbol is used to identify the standard error of M? A. σm B. µ C. σ D. Mm

A

what term is used to identify the mean of the distribution of sample means? A. the expected value of M B. the standard error of M C. the sample mean D. the central limit mean

A

which of the following accurately describes an independent measures study? A. it uses a different group of participants for each of the treatment conditions being comapred B. it uses the same group of participants in all of the treatment conditions being comapred C. it uses one group of participants to evaluate a hypothesis about one pop. mean D. none of the other alternatives are correct

A

which of the following accurately describes the critical region? A. outcomes with a very low probability if the null hypothesis is true B. outcomes with a high probability if the null hypothesis is true C. outcomes with a very low probability whether or not the null hypothesis is true D. outcomes with a high probability whether or not the null hypothesis is true

A

which of the following z score values represents the location closest to the mean? A. z= +0.50 B. z= +1.00 C. z= -1.00 D. z= -2.00

A

which set of characteristics will produce the smallest value for the estimated standard error? A. a large sample size and a small sample variance B. a large sample size and a large sample variance C. a small sample size and a small sample variance D. a small sample size and a large sample variance

A

with a=.05 and a sample of n=15 participants in a repeated measures study comparing 2 treatments, what are the t stat. boundaries for the 2 tailed critical region? A. t= +/-2.145 B. t= +/-1.761 C. t= +/-1.746 D. t= +/-2.120

A

a researcher is measuring problem solving times for a sample of 20 children. However, one of the children fails to solve the problem so the researcher has an undetermined score. What is the best measure of central tendency for these data? A. mean B. median C. mode D. central tendency cannot be determined from this data

B

an independent measures study comparing 2 treatment conditions produces a t stat. with df=18. if the 2 samples are the same size, hiow many participants were in each of the samples? A. 9 B. 10 C. 19 D. 20

B

for an experiment comparing two treatments, an independent measures design would obtain______score(s) for each subject and a repeated measures design would obtain_____score(s) for each subject A. 1,1 B. 1,2 C. 2,1 D. 2,2

B

for the repeated measures t stat., df= A. n1+n2-2 B. n-1 C. (n1-1)+(n2-2) D. n1+n2-1

B

for which of the following situations would a related measures research design be appropriate? A. comparing mathematical skills for girls vs boys at age 10 B. comparing pain tolerance with and without acupuncture needles C. comparing self esteem for students who participate in school athletics vs those who dont D. comparing verbal solving skills for science majors vs art majors at a college

B

in general, if the variance of the difference scores increases, then what will happen to the value of the t stat.? A. it will increase (move farther toward the tail of the dist.) B. it will decrease (move toward the center of the dist.) C. it will stay the same-the t stat. is not affected by the variance of the diff. scores D. it may increase or may decrease. there is no consistent relationship b/w variance and the size of the t stat.

B

on average, what value is expected for the F ratio if the null hypohesis is true? A.0 B. 1.00 C. k-1 D. N-k

B

the following data were obtained from a repeated measures research study. What is the value of SS for the difference scores? subject 1st 2nd #1 10 11 #2 4 6 #3 7 9 #4 6 5 A. 10 B. 6 C. 4 D. 1

B

under what circumstances are post hoc tests necessary? A. when you reject the null with exactly 2 treatment conditions B. when you reject the null with more than 2 treatment conditions C. when you fail to reject the null with exactly 2 treatment conditions D. when you fail to reject the null with more than 2 treatment conditions

B

what happens to the standard error of M as sample size increases? A. it also increases B. it decreases C. it stays constant

B

what proportion of a normal dist. is located in the tail beyond z=2.00? A. 0.9772 B. 0.0228 C. 0.4772 D. 0.0456

B

which combo of factors will produce a large value for η²? A. large mean differences and large sample variances B. large mean differences and small sample variances C. small mean differences and large sample variances D. Small mean differences and small sample variances

B

which of the following is a fundamental difference b/w the t statistic and a z score? A. the t stat uses the sample mean in place of the population mean B. the t stat uses the sample variance in place of the population variance C. the t stat computes the standard error by dividing the SD by n-1 instead of dividing by n D. all of the above are differences b/w t and z

B

which of the following is the correct null hypothesis for a repeated measures t test? A. MD=0 B. μD=0 C. μ1=μ2 D. M1=M2

B

which of the following samples will produce the largest value for a t stat? Assume each sample has n=10 scores A. MD=5 with SS=20 B. MD=10 with SS=20 C. MD=5 with SS=40 D. MD=10 with SS=40

B

True/False According to the central limit theorem, the expected value for a sample mean becomes smaller, approaching zero, as the sample size approaches infinity

False

True/False One reason for transforming X values into z scores is that the set of z scores will form a normal shaped dist.

False

True/False a group of quiz scores ranges from 3 to 10, but no student had a score of X=5. If the scores are put into a frequency dist. table, X=5 would not be listed in the X column

False

True/False for a 2 tailed t test with a=.05 and a sample of n=16, the boundaries for the critical region are t=+/- 2.120

False

True/False for an independent measures study comparing 2 samples with n=8 in each sample, the t stat. would have df=15

False

True/False for the following data from a repeated measures study, the sample mean difference is MD=4 Participant X1 X2 A 1 7 B 4 8 C 5 3

False

True/False if the sample size is doubled, the standard error will always be cut in half

False

True/False in general, the larger the value of the estimated standard error, the greater the likelihood of rejecting the null

False

True/False A positive z score always corresponds to an X value greater than the mean

True

True/False The unit normal table can be used for any normal dist., no matter what the values are for the mean and standard dev.

True

True/False a correlational study is used to examine the relationship b/w 2 variables but cannot determine whether it is a cause and effect relationship

True

True/False a researcher obtained M=27 for a sample of n=36 scores selected from a popualtion with µ=30 and σ=18. This sample mean corresponds to a z score of z= -1.00

True

True/False a sample mean with a z score value greater than z=3.00 would be considered an extreme, unrepresentative sample

True

True/False if other factors are held constant, the larger the difference b/w the 2 sample means is, the larger the value for the independent measures t stat will be

True

True/False if samples are selected from a normal population, the distribution of sample means will also be normal

True

True/False in a research report, the term "statistically significant" is used to indicate that the null hypothesis was rejected

True

True/False once a set of scores has been placed in a grouped frequency dist. table, it is impossible to determine the exact values of the original scores

True

True/False rejecting the null hypothesis with a=.01 means that you have more confidence in your decision than if you had rejected the null hypothesis with a=.05

True

True/False students in an intro art class are classified as art majors and non art majors. this is an example of a measurement on a nominal scale

True

True/False the goal for an experiment is to demonstrate that changes in one variable are responsible for causing changes in a second variable

True

A characteristic, usually a numerical value, that describes a sample is called a_______ A. parameter B. statistic C. variable D. constant

B

A vertical line is drawn through a normal distribution at z = 0.80. What proportion of the distribution is on the right hand side of the line? A. 0.7881 B. 0.2119 C. 0.2881 D. 0.5762

B

Last week Tom had exams in Statistics and in English. He scored 10 points above the mean on both exams. From this information, what can you can conclude about the z-scores for Tom's two scores? A. tom has identical z scores for the 2 exams B. both of tom's z scores are positive C. tom will have a higher z score for the exam with the lower mean D. none of the other choices is correct

B

When n is small (less than 30), how does the shape of the t distribution compare to the normal distribution? A. it is almost perfectly normal B. it is flatter and more spread out than the normal distribution C. it is taller and narrower than the normal dist. D. there is no consistent relationship b/w the t dist. and the normal dist.

B

a hypothesis test with a sample of n=25 participants produces a t stat. of t=+2.53. Assuming a one tailed test with the critical region in the right hand tail, what is the correct decision? A. the researcher can reject the null hypothesis with a=.05 but not with a=.01 B. the researcher can reject the null hypothesis with either a=.05 or a=.01 C. the researcher must FTR the null hypothesis with either a=.05 or a=.01 D. it is impossible to make a decision about H0 without more info

B

a normal distribution has a mean of 24 with a SD of 3. What is the minnimum score needed to be in the top 14% of the dist.? A. X=20.76 B. X=27.24 C. X=25.08 D. X=24.42

B

a population with μ=85 and σ=12 is transformed into z scores. After the transformation, what is the SD for the population of z scores? A. σ=12 B. σ=1.00 C. σ=0 D. cannot be determined

B

For an experiment comparing more than two treatment conditions, why should you use analysis of variance rather than separate t tests? A. separate t tests would require substantially more computations B. a test based on variances is more sensitive than a test based on means C. conducting several t tests would inflate the risk of type I error D. there is no difference b/w the 2 tests, you can use either one

C

If an analysis of variance is used for the following data, what would be the effect of changing the value of SS1 to 50? Sample Data M1 = 10 M2 = 15 SS1 = 90 SS2 = 70 A. increase SSw/in and increase the size of the F ratio B. increase SSw/in and decrease the size of the F ratio C. decrease SSw/in and increase the size of the F ratio D. decrease SSw/in and decrease the size of the F ratio

C

If other factors are held constant, what is the effect of increasing the sample size? A. it will increase the estimated standard error and increase the likelihood of rejecting H0 B. it will increase the estimated standard error and decrease the likelihood of rejecting H0 C. it will decrease the estimated standard error and increase the likelihood of rejecting H0 D. it will decrease the estimated standard error and decrease the likelihood of rejecting H0

C

Samples of size n = 4 are selected from a population with a mean of 80 and standard deviation of 8. What is the standard error for the distribution of sample means? A. 80 B. 8 C. 4 D. 2

C

The students in a psychology class seemed to think that the midterm exam was very easy. If they are correct, what is the most likely shape for the distribution of exam scores? A. symmetrical B. positively skewed C. negatively skewed D. normal

C

Which of the following is a continuous variable? A. eye color of each student in a psych class B. the # of psych majors in each class offered at the college C. the amount of time to solve a problem D. # of children in a family

C

a population dist. has σ=6. What position in this distribution is identified by a z score of +2? A. 2pts above the mean B. 2pts below the mean C. 12pts above the mean D. 12pts below the mean

C

a researcher measures eye color for a sample of 50 ppl. Which measure of central tendency would be appropriate to summarize the measurement? A. mean B. median C. mode D. any of the above

C

a very bright student is described as having an IQ that is 3 SD's above the mean. If this students IQ is reported as a z score, what would the z score be? A. z=μ+3 B. z=μ+3σ C. z=3 D. cannot be determined

C

for an independent measures study, what is measured by cohen's d or r²? A. the risk of type I error B. the risk of type II error C. the size of the difference b/w the 2 treatments D. whether the difference b/w the 2 treatments is likely to have occurred by chance

C

in general, what is the relationship b/w SD and variance? A. SD = the squared variance B. variance is the square root of SD C. SD is the square root of variance D. the 2 measures are unrelated

C

one item on a questionnaire asks, "how many siblings did you have when you were a child?" A researcher computes the mean, median, and mode for a set of 50 responses to this question. Which of the following statements accurately describes the measures of central tendency? A. Because the scores are all whole numbers, the mean will be a whole number B. Because the scores are all whole numbers, the median will be a whole number C. Because the scores are all whole numbers, the mode will be a whole number D. B & C

C

one sample has 4 scores and M=10. A second sample has 6 scores and M=5. If the samples are combined, then what is the mean for the combined sample? A. 7.5 B. 11.67 C. 7 D. cannot be determined

C

organizing a set of scores into a table or graph would be an example of using______ A. population B. sample C. descriptive D. inferential

C

the alternative hypothesis for an independent measures t test states_____ A. there is no mean difference b/w the two populations being compared B. there is no mean difference b/w the two samples being compared C. there is a non zero mean difference b/w the two populations being compared D. there is a non zero mean difference b/w the two samples being compared

C

the average verbal SAT score for the entire class of entering freshman is 530. However, if you select a group of 20 freshman and compute their average verbal SAT score you probably will not get exactly 530. What statistical concept is used to explain the natural difference that exists b/w a sample mean and the corresponding population mean? A. Statistical error B. inferential error C. sampling error D. parametric error

C

what is assumed by the homogeneity of variance assumption? A. the 2 samples have = variances B. the 2 sample variances are not = C. the 2 populations have = variances D. the 2 population variances are not =

C

which combination of factors will produce the smallest value for the standard error? A. a large sample and a large SD B. a small sample and a large SD C. a large sample and a small SD D. a small sample and a small SD

C

which of the following accurately describes a hypothesis test? 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 info about a population to make predictions about a sample

C

which of the following symbols identifies the population SD? A. s B. s² C. σ D. σ²

C

with a = .01 the two-tailed critical region for a t test using a sample of n=16 subjects would have boundaries of_____ A. t=+/- 2.602 B. t=+/- 2.583 C. t=+/- 2.947 D. t=+/- 2.921

C

Determining a person's reaction time (in milliseconds) would involve measurement on a(n) _____ scale of measurement. A. nominal B. ordinal C. interval D. ratio

D

For any distribution, what is the z-score corresponding to the median? A. 0 B. 1 C. N D. cannot be determined

D

In a correlational study A. 1 variable is measured and 2 groups are compared B. 2 variables are measured and 2 groups are compared C. 1 variable is measured and there is only 1 group of participants D. 2 variables are measured and there is only 1 group of participants

D

John drives to work each morning and the trip takes an average of µ = 38 minutes. The distribution of driving times is approximately normal with a standard deviation of σ = 5 minutes. For a randomly selected morning, what is the probability that John's drive to work will take less than 35 minutes?​ A. 0.6554 B. 0.3446 C. 0.7257 D. 0.2743

D

What was the final step to be performed in the following mathematical expression? (ΣX)² ? A. square each score B. add the scores C. add the squared scores D. square the sum of the scores

D

a sample of n=25 individuals is selected from a population with µ =80 and a treatment is administered to the sample. What is expected if the treatment has no effect? 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 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 to 80 and should lead you to fail to reject the null hypothesis

D

if a repeated measures study shows a significant difference b/w 2 treatments with a=.01, then you can be sure that_____ A. the value of cohen's d is large B. the % of variance explained (r²) is large C. both cohen's d and r² are large D. a significant effect doesnt necessarily mean that the effect size will be large

D

the z-score boundaries for the critical region are determined by_____ A. the null hypothesis B. the sample data C. the size of the standard error D. the alpha level

D

under what circumstances would a score that is 15 pts above the mean be considered an extreme score? A. when the population mean is much larger than 15 B. when the population SD is much larger than 15 C. when the population mean is much smaller than 15 D. when the population SD is much smaller than 15

D

what frequency distribution graph is appropriate for scores measured on a nominal scale? A. only a histogram B. only a polygon C. either a histogram or a polygon D. only a bar graph

D

which of the following are requirements of a random sample? A. every individual has an equal chance of being selected B. the probabilities cannot change during a series of selections C. there must be sampling with replacement D. All of the other 3 choices are correct

D