PSY 418 Exam Questions

what proportion of a normal distribution falls between z= -1.96 and z= +1.96?

0.9500

for the AxB summation equation, assume that factor A has 3 levels and factor B has 5 levels. After calculating the squared result for i=1, and j=4, what is the value for i for the next (upcoming) iteration?

1

a population of scores has μ = 50 and σ= 12. If you subtract 1 point from every score in the population, then the new standard deviation will be:

12

in the frequency distribution table below, what is the percentile rank of x=10?

13%

an analysis of variance produces SSbetween= 30, SSwithin= 60, and an F-ration with df=2,15. For this analysis, what is the F-ratio?

15/4= 3.75

on a 40-item exam, in which each item contains four possibilities, you get 16 correct. You test the 2-tailed null hypothesis which claims that the likelihood of getting an item correct is .25. What is the z-calc

2.22

as sample of n=25 scores is determined to have a standard error of 4 points What is the standard deviation from the population from which the sample was obtained?

20

the follower are three rows from a frequency distribution table. For this distribution, what is the percentile rank of x=16.6?

23.4%

for the AxB summation equation, assume that factor A has 3 levels and factor B has 5 levels. After calculating the squared result for i=2, and j=5, what is the value for i for the next (upcoming) iteration?

3

for an independent-measures ANOVA comparing three treatments with a sample of n=5 in each treatment, what is the critical value for the F-ration using α=.05?

3.88

for a normal distribution with μ= 500 and σ = 100, what is the minimum score necessary to be in the top 90% of the distribution?

375

the following table shows the results of an analysis of variance comparing four treatment conditions with a sample of n=5 participants in each treatment. Note that several values are missing in the table. What is the missing value for the F-ratio? Between SS: 30 Within SS: X Total SS: 62 Between df: X Within df: X Total df: X Between MS: X Within MS: X F=X

5.00

for the following data, what is the value of SSwithin? SS=10 SS=20 SS=10 SS=20

60

the average amount of time spent watching TV for the general population of 8 to 12 year-old children is hypothesized to be μ = 4.1 hours/day. Recent results indicate that children with ADHD tend to watch more TV than children who are not diagnosed with the disorder, which suggests using a one-tailed test to evaluate the null hypothesis. To test the null, a researcher obtains a random sample of n = 64 children, 8 to 12 years old, who have been diagnosed with ADHD. Parents are asked to keep a journal recording how much time each day is spent watching TV. The average daily time for the sample is M = 4.5 hours, with a sample standard deviation of s = 4.0 hours. How many degrees of freedom are used for this test?

63

the following table shows the results of an analysis of variance comparing three treatment conditions with a sample of n=10 participants in each treatment. Note that several values are missing in the table. What is the missing value for SStotal? Between SS: 20 Within SS: X Total SS: X Between df: X Within df: X Total: X Between MS: X Within MS: 2 F: X

74

if the sample size is held constant, which of the following will produce the widest 90% confidence interval for the population mean difference for a repeated-measures study?

MD = 3 with s2 = 20 for the difference scores

in a two-tailed z-test, why is ±1.96 important? a. ±1.96 has a p-value of .05 b. ±1.96 has a p-value of .025 c. A test statistic of equal or greater extremity results in rejection of the null hypothesis

more than one of the above is correct

two separate samples are being used to estimate the population mean difference between the two treatment conditions. Which of the following would produce the widest confidence interval?

n1=n2=10 with a pooled variance of 100

using z-scores, a population with μ = 47.79 and σ= 6.002 is standardized so that the new mean is μ = 50.902 and σ= 1.128. How does an individual's z-score in the new distribution compare with his/her z-score in the original population?

new z= old z

which of the following is an advantage of transforming x-values into z-scores? a. all negative numbers are eliminated b. all scores are moved closer to the mean c. the distribution is transformed to a normal distribution d. none of the other options is an advantage

none of the other options is an advantage

in general, how are degrees of freedom obtained?

number of deviations minus one

which of the following accurately describes the chi-square distribution?

positively skewed with all values greater than or equal to zero

in a two-factor ANOVA, what is the implication of a significant AxB interaction for the main effects?

the significance of the interaction has no implications for the main effects

in a 2-factor ANOVA with 2 levels of the A factor, if Ma1=5 and Ma2=6, what can you conclude if the grand mean is equal to 5.2?

the two sample sizes are not equal

what does the standard error of the proportion describe?

the variability of the distribution of sample proportions

a researcher uses a repeated-measures design to compare individuals' performance before treatment with their performance after treatment. If all of the participants show improved performance of 8 or 9 points after treatment, then the researcher should find:

the variance of the difference scores is near zero

what is stated by the null hypothesis (Ho) for an ANOVA?

there are no differences between any of the population means

why do we divide SS by df?

to convert SS into a statistic

true or false: as df increases, the student's t distribution approaches a normal distribution

true

true or false: as sample size decreases, the estimated standard error increases

true

true or false: for a hypothesis test using a t-statistic, the boundaries for the critical region will change if the sample size is changed (assume that the alpha level is held constant)

true

true or false: in general, an increase in the sample variance makes it less likely that the t-statistic will be large enough to reject the null hypothesis

true

true or false: in general, the larger the value of the estimated standard error, the lower the likelihood of rejecting the null hypothesis

true

true or false: statistical power plus the likelihood of type II error always equals 1.0

true

true or false: within any normal or symmetrical distribution of scores, the location specified by z= +.1 and the location specified by z= -.1 are exactly the same distance from the mean

true

assume that the 95% confidence interval around a sample proportion ranges from .4 to .6. What can we infer?

we can be 95% confident that the population proportion lies in this interval

what is the value of test statistic (aka, t-calc)?

.08

assuming that the null hypothesis is true, what is the probability of obtaining a sample that generates a z-value at least as extreme as z=-1.19?

.234

what is the probability of getting at least 12 questions correct by blindly guessing on a 40 term exam, in which each item contains four possibilities?

.2912

if a hypothesis test is found to have power= .70, then what is the probability that the test will result in a type II error?

.30

a test statistic of z=-2.88 was calculated. Estimate the p-value:

.4%

describe the 95% confidence interval of the population proportion with a sample proportion of .5 and a sample size of 25?

.5 ±.196

assuming that the null hypothesis is true, what is the likelihood of obtaining a sample mean as least as extreme as one that produces a z-score of 2.58?

.98%

assuming no interaction, what does the following equation total to? (equation for SSAxB)

0

in a chi-square test for independence of goodness of fit:

both Σfe=n and Σfe=Σfo

which of the following will increase the power of a statistical test?

change the sample size from n=25 to n=100

if an analysis of variance is used for the following data, what would be the effect of changing the value of M1 to 20? M1=15 M2=25 SS1=90 SS2=70

decrease SSbetween and decrease the size of the F-ratio

in general, decreasing the alpha level (for example, from .05 to .01) will:

decrease the likelihood of rejecting Ho and decrease the risk of type I error

which of the following confidence intervals also indicates a significant difference between treatments with α=.05?

estimate that μ1 - μ2 is in an interval between 2 and 10 with 95% confidence

which of the following confidence intervals also indicates a significant two-tailed difference between treatments with α level of .05?

estimate that μ1 - μ2 is in an interval between 2 and 10 with 99% confidence

true or false: a score with a value higher than the mean will have a negative z-score

false

true or false: distribution of sample means (sampling distributions) are normal when they are based on samples of at least n=30

false

true or false: it is impossible for fewer than half of the scores in a distribution to have values greater than the mean

false

true or false: you are more likely to make a type I error with a sample of n=4,000 than with a sample of n=100,000,000

false

in general, increasing the sample size (for example, from n=4 to n=50) will ____________ the risk of type I error (assuming α is held constant .05)

have no influence on

if two samples are selected from the same population and are testing the same null hypothesis

if the samples are the same size, have the same sample mean, and have the sample sample variance

with α=.01 and df=25, the critical value for a one-tailed t-test is t=2.485. Assuming all other factors are held constant, if the df value were decreased, the critical value of t would:

increase

if an analysis of variance is used for the following data, what would be the effect of changing the value of SS2 to 100? M1=15 M2=25 SS1=90 SS=70

increase SSwithin and decrease the size of the F-ratio

for a fixed level of significance, the critical value for chi-square will:

increase as the sample size increases

for an independent-measures t-statistic, what is the effect of increasing the number of scores in the samples?

increase the likelihood rejecting the Ho and increase measures of the effect size

a researcher is predicting that a treatment will decrease scores. If this treatment is evaluated using a directional hypothesis test, then the critical region for the test:

is in the left-hand tail of the distribution

if the mean and variance are computed for each sample in an independent-measures two-factor experiment, then which of the following types of sample data will tend to produce large D-ratios for the two-factor ANOVA?

large differences between sample means and small sample variances

assuming that the null hypothesis is true, what is the likelihood of obtaining a sample mean as least as extreme as one that produces a t(30) score of -2.58?

lower than 2%, but greater than 1%

a test statistic of t(10)=2.5 was calculated. Estimate the p-value:

lower than 4%, greater than 2%

what is the estimated p-value of the test statistic?

lower than 50% and greater than 40%

in the table used to asses the test statistic, what does the vertical line in the right tail of the F distribution indicate when alpha=.05?

the 95th percentile

the z-score boundaries for the critical regions in a hypothesis test are determined by:

the alpha level

what happens to the critical value for a chi-square test if the number of categories is increased?

the critical value also increases

what happens to the critical value for a chi-square test if the size of the sample is increased?

the critical value depends on the number of categories, not the sample size

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?

the mean

what value is estimated with a confidence interval using the repeated-measures t-statistic?

the mean for a population of difference scores

a one-tailed, directional test has a critical value (value needed to reject the null hypothesis) of 1.645 (alpha=.05). Based on this information, it is probably safe to assume that:

the population standard deviation is known

which of the following is an accurate definition for the power of a statistical test?

the probability of rejecting a false hypothesis

from the table above, what is the 40th percentile?

x=19.0

what is the 77.5th percentile in the frequency distribution table below?

x=22.0

on a 40-item exam, in which each item contains four possibilities, you get 16 correct. Does this allow you to reject the 2-tailed null hypothesis which claims that the likelihood of getting an item correct is .25?

yes

for any normal distribution, what are the z-score values that form the boundaries for the middle 74%?

z= +/- 1.13

a population has μ = 50 and σ= 5. If every score in the population is multiplied by 3, then what are the new values for the mean and standard deviation?

μ = 150 and σ= 15

which of the following is the correct null hypothesis for an independent-measures t-test?

μ1 - μ2 = 0

which of the following is the correct null hypothesis for a repeated t test?

μD = 0