EDPS TEST 2
effect size: small - medium - large -
.2 .5 .8
power =
1 - B
Calculate the following percentages for a z score of 0.74, with a tail of 22.96%. a. What percentage of scores falls below this z score?
100-22.96 = 77.04
Calculate the following percentages for a z score of 0.74, with a tail of 22.96% c. What proportion of scores falls below a z score of -0.74?
22.966 = .2296
Calculate the following percentages for a z score of 0.74, with a tail of 22.96%. b. What percentage of scores falls between the mean and this z score?
59-22.96 = 27.04
Null hypothesis symbols: words:
H0 = u1 - u2 there will be no difference in the mean of population 1 to the mean of population 2
research hypothesis symbols: words:
H1 = u1 /= u2 there will be a difference in the mean of population 1 to the mean of population 2
21. If a hypothesis test is found to have a power = 0.70, then what is the probability that the test will result in a Type II error? a) 0.30 b) 0.70 c) 0.05 d) It cannot be determined without more information.
a) 0.30
11. For a repeated-measures study comparing two treatments, a researcher obtains a sample of N = 9 difference scores with a Mdifference = 4 and a variance of s2 = 36. What is the value for the t statistic for these data? a) 2 b) .67 c) .33 d) .11
a) 2
16. _____ is a measure of our ability to reject the null hypothesis given that the null hypothesis is false. a) Statistical power b) Eta squared c) Cohen's d d) R2
a) Statistical power
12. Paired-samples t tests are particularly well suited to research studies that examine learning or other changes that occur over time. a) True b) False
a) True
13. In a repeated-measures study, a small variance for the difference scores indicates that the treatment effect is consistent across participants. a) True b) False
a) True
18. If a hypothesis test using a sample of n = 15 scores produces a t statistic of t = 2.15, then the correct decision is to reject the null hypothesis for a two-tailed test with an a of .05. a) True b) False
a) True
19. The null hypothesis is stated in terms of the population even though the data come from a sample. a) True b) False
a) True
8. The null hypothesis predicts that there is no effect for our manipulation or that there is no difference between groups. a) True b) False
a) True
20. When using an independent-samples t test, we have to create a: a) distribution of differences between means. b) difference score for each participant. c) distribution of differences between raw scores. d) distribution of mean differences.
a) distribution of differences between means.
25. If a t score is calculated to be -.03 and our critical values are -2.365 and 2.365, what decision do we make about our research study? a) fail to reject the null hypothesis b) reject the null hypothesis c) accept the null hypothesis d) accept the research hypothesis
a) fail to reject the null hypothesis
18. Name three ways to increase statistical power a) increase your alpha, turn a two-tailed hypothesis into a one-tailed hypothesis, and increase N b) use nonparametric statistics, increase your beta, and increase your N c) turn a two-tailed hypothesis into a one-tailed hypothesis, increase your alpha levels, and decrease N d) increase your alpha levels, increase your beta levels, and increase N
a) increase your alpha, turn a two-tailed hypothesis into a one-tailed hypothesis, and increase N
12. A(n) _____ is based on our sample statistic; it conveys the range of sample statistics we could expect if we conducted repeated hypothesis tests using samples from the same population. a) interval estimate b) point estimate c) coefficient of determination d) estimated standard error
a) interval estimate
15. The fact that a research participant encounters the dependent variable twice in a within-groups design means that we have to be concerned about: a) order effects. b) using statistics. c) compensating participants. d) gender differences.
a) order effects.
22. It is hypothesized that there is a significant difference in depression levels between men and woman in a college dormitory. This hypothesis best illustrates a: a) research hypothesis. b) null hypothesis. c) standardized hypothesis. d) directional hypothesis.
a) research hypothesis.
1. A(n) _____ is a type of t test in which we compare data from one sample to a population for which we know the mean but not the standard deviation. a) single-sample t test b) nonparametric t test c) independent-samples t test d) dependent-samples t test
a) single-sample t test
confidence interval
an estimate that spans an interval (range) based upon a sample statistics (normally 95%)
5. The figure below demonstrates the concept of converting a given percentile to a raw score for a student who scored in the 63rd percentile; 13% corresponds to the associated percentage that results from subtracting the area below the mean from the 63rd percentile. What is the associated z score? a) 0.67 b) 0.33 c) 0 d) 13
b) 0.33
17. For a paired-samples t test, Mdifference = 47 and s = 7, N = 16, the 95% confidence interval is: a) 32.08 to 61.92 b) 43.27 to 50.73 c) 43.15 to 50.85 d) none of the above
b) 43.27 to 50.73
19. An independent-samples t test is used with which type of research design? a) A within-groups design b) A between-groups design c) A paired-samples design d) A single-sample design
b) A between-groups design
17. Power is the probability that we will not make a Type I error. a) True b) False
b) False
24. When determining the critical value for an independent-samples t test, you use the degrees of freedom for the smaller sample. a) True b) False
b) False
4. In general, the larger the value of the sample variance, the greater the likelihood of rejecting the null hypothesis. a) True b) False
b) False
5. 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 distribution. d) There is no consistent relationships between the t distribution and the normal distribution.
b) It is flatter and more spread out than the normal distribution.
3. What is the difference between the z and t tests? a) The z test uses the estimated standard error while the t statistic uses the actual standard error of the population of means. b) The t test uses the estimated standard error while the z statistic uses the actual standard error of the population of means. c) The z test uses the estimated standard deviation while the t statistic uses the actual standard deviation. d) The t test uses the estimated standard deviation while the z statistic uses the actual standard deviation.
b) The t test uses the estimated standard error while the z statistic uses the actual standard error of the population of means.
7. With α = .05 and df = 8, the critical values for a two-tailed test are t = ± 2.306. Assuming that all other factors are held constant, if the df value were increased to df = 20, what would happen to the critical values for t? a) They would increase (move farther from zero). b) They would decrease (move closer to zero). c) They would stay the same. d) There is not enough information provided to answer this question.
b) They would decrease (move closer to zero).
27. Why is it necessary to use the pooled variance when conducting an independent-samples t test? a) Using the pooled variance helps the researcher identify skewness. b) We are working with two samples and an estimate of spread based on two samples is likely to be more accurate than an estimate of spread based on a single sample. c) It is necessary to estimate the standard deviation of the two samples in order to compare the two samples to one another. d) Estimating the spread of the sample using the standard deviation increases the generalizability of results.
b) We are working with two samples and an estimate of spread based on two samples is likely to be more accurate than an estimate of spread based on a single sample.
20. If the treatment has a very small effect, then what is the likely outcome for a hypothesis test evaluating the treatment? a) a Type I error b) a Type II error c) a correct rejection of the null hypothesis d) a correct failure to reject the null hypothesis
b) a Type II error
2. As sample size decreases, the shape of the t distribution: a) gets progressively narrower. b) gets progressively wider. c) more closely matches the z distribution. d) is more accurate.
b) gets progressively wider.
8. Under what circumstances can a very small treatment effect be statistically significant? a) if the sample size is big and the sample variance is also big b) if the sample size is big and the sample variance is small c) if the sample size is small and the sample variance is big d) if the sample size and the sample standard deviation are both small
b) if the sample size is big and the sample variance is small
7. A researcher hypothesizes that there is a significant relationship between stress and fatigue. Specifically, he hypothesizes that as stress increases, fatigue levels will also increase. This example best illustrates what type of hypothesis test? a) null hypothesis test b) one-tailed test c) two-tailed test d) nondirectional test
b) one-tailed test
11. A(n) _____ is a summary statistic from a sample that is just one number which serves as an estimate of the population parameter. a) interval estimate b) point estimate c) coefficient of determination d) estimated standard error
b) point estimate
23. The weighted average of the two estimates of variance (one from each sample) that are calculated when conducting an independent-samples t test is referred to as: a) standard error. b) pooled variance. c) degrees of freedom. d) the confidence interval.
b) pooled variance.
1. If Laura received a z score of 1 for her performance on a standardized math test, approximately what percentage of scores are below her score? a) 34% b) -34% c) 84% d) -84%
c) 84%
15. A treatment is administered to a sample of N = 9 individuals selected from a population with a mean of M = 80 and a standard deviation of s = 12. After treatment, the effect size is measured by computing Cohen's d, and a value of d = 0.50 is obtained. Based on this information what is the mean for the treated smaple? a) 6 b) 82 c) 86 d) it cannot be determined based on the information provided
c) 86
13. What measure of effect size assesses the difference between two means in terms of standard deviation? a) statistical power b) eta squared c) Cohen's d d) R2
c) Cohen's d
14. To calculate effect size for a paired-samples t test we use: a) eta squared. b) the p statistic. c) Cohen's d. d) the z statistic.
c) Cohen's d.
16. Dependent sampling generally results in a more powerful statistical test than independent sampling because: a) the dependent procedure generally has a larger N. b) dependent procedures have higher acceptable levels of c) dependent procedures reduce the variability in the sampling distribution. d) All of these are correct.
c) dependent procedures reduce the variability in the sampling distribution.
6. What are the three assumptions for hypothesis testing? a) independent variable is measured on an interval scale, participants are based on a convenience sample, and the population distribution is approximately normal b) extraneous variables are controlled for, random selection of participants, and random assignment to levels of the independent variable. c) dependent variable is measured on an interval or ratio scale, participants are randomly selected, and population distribution is approximately normal d) variables are all continuous, variables are measured on a ratio scale of measurement, and participants are randomly selected
c) dependent variable is measured on an interval or ratio scale, participants are randomly selected, and population distribution is approximately normal
10. A paired-samples t test is also known as a(n): a) single-sample t test. b) independent-samples t test. c) dependent-samples t test. d) confidence interval.
c) dependent-samples t test.
14. What is the correct formula for Cohen's d for a z statistic? a) 𝑑 = (𝑋1−𝑋2)+(𝑀1+𝑀2)/𝑅2 b) 𝑑 = (𝑀𝑥−𝑀𝑦)−(𝜇𝑥−𝜇𝑦)/ 𝑠𝑝𝑜𝑜𝑙𝑒𝑑 c) 𝑑 = (𝑀−𝜇)/ 𝜎 d) 𝑑 = (𝑀1−𝑀2)−(𝜇1−𝜇2)/ sdifference
c) 𝑑 = (𝑀−𝜇)/ 𝜎
a =
chance of making a type I error (p level)
B =
chance of making a type II error
3. Roberta scored in the 85th percentile on a standardized test of reading ability. What is Roberta's associated z score? a) -1.04 b) 2.30 c) 3.10 d) 1.04
d) 1.04
4. If we obtain a z score of 2.5, what is our raw score for a given population mean of 800 and a standard deviation of 100? a) 840 b) 2100 c) 900 d) 1050
d) 1050
9. It is hypothesized that there will be a significant difference in aggression scores after caffeine consumption as compared to before caffeine consumption. This hypothesis best illustrates what type of t test? a) a single-sample t test b) a nonparametric t test c) an independent-samples t test d) a paired-samples t test
d) a paired-samples t test
26. The comparison distribution for an independent-samples t test is a distribution of: a) means. b) scores. c) mean difference scores. d) differences between means.
d) differences between means.
21. When conducting a study of gender differences, we have to employ a(n): a) single-sample t test. b) paired-samples t test. c) dependent-samples t test. d) independent-samples t test.
d) independent-samples t test.
6. Researchers examined the impact of candy on students' test performance and found that candy significantly increased test performance. When they examined the effect size, they found that Cohen's d was .02. Based on convention this is considered: a) small. b) medium. c) large. d) too small to be of interest.
d) too small to be of interest.
2. A distribution of z scores has a known mean and standard deviation. What are they? a)Mean = 100, SD=15 b)Mean = 0, SD=3 c)Mean = 50, SD= 1 d)Mean = 0, SD = 1
d)Mean = 0, SD = 1
as power increases, overlap _______ which means you are _______ likely to make a type II error
decreases less
degrees of freedom
df = N - 1
between groups design
different people before and after IV
indépendant samples t test distribution:
distribution of differences between means
paired samples t test distribution:
distribution of mean differences
the greater the distance between means, the _______ the effect size
greater
factors that increase power
increase alpha make a two-tailed test a one-tailed increase N exaggerate mean differences decrease SD
increase sample size = __________ in test statistic
increase in test statistic
as power decreases, overlap _______ which means you are _______ likely to make a type II error
increases more
between groups design names
indépendant samples t test
reject the null hypothesis when z statistics _________ the critical region
is in
reject the null hypothesis when z statistics _________ the critical region
is not in
less overlap = ______ effect size = data is
large meaningful and important
single sample t test compares sample to a population in which we know the ________ but not the __________ _________ of the population
mean standard deviation
if you have the general population standard deviation you use
more than 30 = z score less than 30 = t score
large sample size = what kind of curve
narrow and tall
within groups design names
paired samples t test repeated measures dependent samples
within groups design
same people before and after IV
single sample t test compares
sample to a population
if you do not have the general population standard deviation you use
t score
critical region
the area in the tails of the comparison distribution in which we reject the null hypothesis
statistical power
the chance of NOT making a type II error
small sample size = what kind of curve
wide and flat curve