psych 138 TEST #3

A researcher interested in the use of discipline practices by males versus females predicted that men would use power oriented practices more frequently than women. The research or experimental hypothesis would be that

men use power techniques more than women.

one-tailed hypothesis

only one direction of an effect or relationship is predicted in the alternative hypothesis of the test

On average, what value is expected for the t statistic when the null hypothesis is true?

0

When the null hypothesis is true, the t statistic will have an average value of ______.

0

One sample of n = 5 scores has SS = 36. A second sample of n = 7 scores has SS = 64. What is the value of the pooled variance for these two samples?

100/10

A sample of n = 4 difference scores produces SS = 48. What is the estimated standard error for the sample mean difference?

2 find the sample variance SS/n-1 estimated standard error= under square root (sample variance/ n) = 2

A researcher reports t(24) = 5.30 for an independent-measures experiment. How many individuals participated in the entire experiment?

26

The results of an independent-measures study produce a t statistic with df = 36. How many individual participated in the entire study?

38

The research hypothesis states that the A. independent variable had no effect. B. independent variable did have an effect. C. dependent variable had no effect. D. dependent variable did have an effect.

B. independent variable did have an effect.

Which of the following statements is most accurate about hypothesis testing? A. It is a central theme in the statistical analysis of virtually all psychology research. B. It is a simple part of statistics that only applies to three statistical procedures. C. It is a fairly uncommon way of using statistics. D. It is a kind of statistical procedure that is used mainly as part of descriptive statistics.

A. It is a central theme in the statistical analysis of virtually all psychology research.

Which set of sample characteristics is most likely to produce a significant t statistic (reject H0)? 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. a large sample size and a small sample variance

The variance of a distribution of sample means of more than one is A. smaller than the original population variance. B. the same as the original population variance. C. greater than the original population variance. D. unrelated to the original population variance.

A. smaller than the original population variance.

With α = .05, what is the critical t value for a one-tailed test with n = 25? A. t = 1.711 B. t = 2.064 C. t = 2.708 D. t = 2.060

A. t = 1.711

An independent-measures study ______. A. uses a different sample for each of the different treatment conditions being compared. B. use the same sample for each of the different treatment conditions being compared. C. uses the data from one sample to evaluate a hypothesis about the population mean. D. none of the other alternatives is correct

A. uses a different sample for each of the different treatment conditions being compared.

A repeated-measures study would not be appropriate for which of the following situations? A. A researcher would like to study the effect of practice on performance. B. A researcher would like to compare individuals from two different populations. C. The effect of a treatment is studied in a small group of individuals with a rare disease. D. A developmental psychologist examines how behavior unfolds by observing the same group of children at different ages.

B. A researcher would like to compare individuals from two different populations.

When is a result considered statistically significant? A. When the sample score is so extreme that the research hypothesis is rejected. B. When the sample score is so extreme that the null hypothesis is rejected. C. When the population mean is so extreme that the research hypothesis is rejected. D. When the population mean is so extreme that the null hypothesis is rejected.

B. When the sample score is so extreme that the null hypothesis is rejected.

How do you set up a hypothesis testing problem? A. You set it up to test what you predict will happen. B. You set it up to test the opposite of what you predict will happen. C. You set up two problems, one to test what you predict and the other to test the opposite. D. You set up a test that assumes the two populations are different, regardless of whether that is what you predict or not.

B. You set it up to test the opposite of what you predict will happen.

A repeated-measures study finds a mean difference of mean of the differences (MD) = 5 points between two treatment conditions. Which of the following sample characteristics is most likely to produce a significant t statistic for the hypothesis test? A. a large sample size (n) and a large variance B. a large sample size (n) and a small variance C. a small sample size (n) and a large variance D. a small sample size (n) and a small variance

B. a large sample size (n) and a small variance

A researcher uses a repeated-measures study to compare two treatment conditions with a set of 20 scores in each treatment. What would be the value of df for the repeated-measures t statistic? A. df = 18 B. df = 19 C. df = 38 D. df = 39

B. df=19

What is measured by the estimated standard error? A. how spread out the scores are in the sample. B. how spread out the scores are in the population. C. how much difference is reasonable to expect between a sample mean and the population mean. D. how much difference is reasonable to expect between the t statistic and the corresponding z-score.

B. how spread out the scores are in the population.

Based on the results of her study, a researcher rejects the null hypothesis because the probability of obtaining her result if the null hypothesis was true is less than 5%. How would this be symbolized? A. p = 5%. B. p < .05. C. .05 < p. D. p > 5%.

B. p < .05.

The results of a hypothesis test are reported as follows: t(29) = 2.70, p < .05. Based on this report, how many individuals were in the sample? A. 28 B. 29 C. 30 D. cannot be determined from the information provided

C. 30

How do you decide whether to reject the null hypothesis? A. If the Z score is less than -1 or greater than +1. B. If the Z score is greater than +2.5. C. Compare the Z score needed to reject the null hypothesis to the actual Z score of the sample. D. Compare the standard deviation of the sample (SD) to the standard deviation of the population ().

C. Compare the Z score needed to reject the null hypothesis to the actual Z score of the sample.

Which of the following is NOT a correct statement of one of the five steps of hypothesis testing? A. Restate the question as a research hypothesis and a null hypothesis about the populations. B. Determine the characteristics of the comparison distribution. C. Determine the cutoff score on the sample's distribution at which the research hypothesis should be rejected. D. Decide whether to reject the null hypothesis.

C. Determine the cutoff score on the sample's distribution at which the research hypothesis should be rejected.

Which of the following research situations is most likely to use an independent-measures design? A. Evaluate the effectiveness of a pain reliever by measuring how much pain is reduced after taking the medication. B. Evaluate the effectiveness of a cholesterol medication by comparing cholesterol levels before and after the medication. C. Evaluate the difference in self-esteem between student athletes and non-athletes D. Evaluate the development of verbal skills between age 2 and age 3 for a sample of girls.

C. Evaluate the difference in self-esteem between student athletes and non-athletes

Which of the following studies uses a matched-subjects design? A. A group of twins is tested for visual acuity on one day and then tested again the following day after receiving a drug. B. A sample of children is tested for vocabulary skills at age six and then again at age ten. C. Participants are assigned to one of two treatment groups so that each participant in one group has the same IQ as a participant in the other group. D. None of the other options is a matched-subjects design.

C. Participants are assigned to one of two treatment groups so that each participant in one group has the same IQ as a participant in the other group.

When a researcher figures the sample's mean in a study, the researcher then compares it to A. the parameters of the known population distribution. B. an estimated distribution based on earlier research findings. C. the distribution of means of all the possible samples in the experimental condition from the research. D. the distribution of sample means that would be found if the null hypothesis were true.

D. the distribution of sample means that would be found if the null hypothesis were true.

The square root of the variance of the distribution of sample means is A. the estimated sample variance. B. the average deviation of the original population. C. an unbiased estimate of the population standard deviation. D. the standard deviation of the distribution of means.

D. the standard deviation of the distribution of means.

The null hypothesis for a repeated-measures test states: A. Each individual will have a difference score of D = 0. B. The overall sample will have a mean difference of MD = 0. C. The entire population will have a mean difference of μD = 0. D. All of the other options are correct.

C. The entire population will have a mean difference of μD = 0.

A researcher is interested in a new kind of exercise. This new exercise can be done by anyone because it does not require any equipment and, therefore could be potentially beneficial, without cost to the person. The researcher is interested in whether this new exercise will reduce the rate of heart attacks in people who do it. What is the alternative (research) hypothesis? A. People will participate because it does not cost them any money. B. The exercise will make no difference in the rate of heart attacks. C. The exercise will reduce the rate of heart attacks. D. The exercise will increase the rate of heart attacks.

C. The exercise will reduce the rate of heart attacks.

The alternative hypothesis for an independent-measures t test states ______. A. There is no mean difference between the two populations being compared. B. There is no mean difference between the two samples being compared. C. There is a non-zero mean difference between the two populations being compared. D. There is a non-zero mean difference between the two samples being compared.

C. There is a non-zero mean difference between the two populations being compared.

In general, an increase in the sample size in a repeated-measures study will cause ______. A. an increase in the standard error and an increase in the value of t B. an increase in the standard error and a decrease in the value of t C. a decrease in the standard error and an increase in the value of t D. a decrease in the standard error and a decrease in the value of t

C. a decrease in the standard error and an increase in the value of t

A Type I error is the result of A. improper measurement techniques on the part of the researcher. B. failing to reject the null hypothesis when, in fact, it is true. C. incorrectly rejecting the null hypothesis. D. incorrectly accepting the null hypothesis.

C. incorrectly rejecting the null hypothesis.

The alpha level is A. usually determined while analyzing experimental data. B. the chance of obtaining an inconclusive result when the research hypothesis is true. C. the probability of a Type I error. D. always set at 1%.

C. the probability of a Type I error.

A sample of n = 9 scores has a mean of M = 46 and a variance = 36. What is the estimated standard error for this sample? A. 12 B. 6 C. 4 D. 2

D. 2

What is a correct argument for using a one-tailed test when there is a clear basis for predicting a result in a given direction? A. The underlying mathematics of one-tailed tests are more accurate. B. If the result is opposite to the prediction, the researcher can still do a two-tailed test later. C. It is more conservative, in the sense that when using a one-tailed test, it is harder to reject the null hypothesis. D. It is less conservative, in the sense that when using a one-tailed test, it is easier to reject the null hypothesis.

D. It is less conservative, in the sense that when using a one-tailed test, it is easier to reject the null hypothesis.

In principal, you could make a distribution of sample means by A. calculating the mean of all the possible samples of a given size and dividing it by the variance. B. using the sample's mean and variance divided by the population's parameters. C. randomly estimating the population variance from the various samples of the same size, and using the sample mean in place of . D. randomly taking a very large number of samples from a population, each of the same size, and making a distribution of their means.

D. randomly taking a very large number of samples from a population, each of the same size, and making a distribution of their means.

Based on her use of inferential statistics, Martha believes that the difference in happiness scores between single versus married women in her study is a true difference. Thus, she would _____ and assume _____. A. accept the null; statistical significance B. accept the null; no statistical significance C. reject the null; no statistical significance D. reject the null; statistical significance

D. reject the null; statistical significance

Central Limit Theorem

For any population with mean μ and standard deviation σ, the distribution of sample means for sample size n will approach a normal distribution with a mean of μ and a standard deviation of (standard deviation/ square root of n) as n approaches infinity (good approximation if n > 30)

As Pop. Stdev gets larger, Standard Error gets ___________ As sample size gets larger, Standard Error gets _______ (Law of large numbers)

Larger, smaller

Type I error (alpha)

concluding that there is a difference between groups ("an effect") when there really isn't

Type II error

concluding that there isn't an effect when there really is

Which combination of factors is most likely to produce a significant value for an independent-measures t statistic?

large samples and small variance

two-tailed hypothesis

both directions of an effect or relationship are considered in the alternative hypothesis of the test

sampling error

expected difference between the sample statistics and the population parameters

What does variance measure?

it measures how far a set of (random) numbers are spread out from their average value

p-value

probability value associated with an inferential test that indicates the likelihood of obtaining the data in a study when the null hypothesis is true

A sample of n = 4 scores has SS = 60. What is the variance for this sample?

ss/ n-1;60/4-1= 20

A sample of n = 25 scores has a mean of M = 40 and a variance = 100. If this sample is being used to test a null hypothesis stating that μ = 43, then what is the t statistic (computed t) for the sample?

t = -0.30

Two samples, each with n = 15 individuals, are used to evaluate the difference between two treatment conditions. If the researcher uses a two-tailed test with α = .05, then the critical region for the t statistic begins at ______.

t = ±2.048

Standard error

the average amount that you'd expect a sample to deviate from the sample mean

alternative hypothesis

the hypothesis that an effect or relationship exists (or exists in a specific direction) in the population

null hypothesis

the hypothesis that there is no significant difference between specified populations, any observed difference being due to sampling or experimental error.

A researcher computes the pooled variance for two samples and obtains a value of 120. If one of the samples has n = 5 scores and the second has n = 10 scores, then what is the value of the estimated standard error for the sample mean difference? A. the square root of (120/15) B. the square root of (120/13) C. the square root of (120/5 + 120/10) D. the square root of (120/4 + 120/9)

the square root of (120/5 + 120/10)

The difference between creating a Z score from a single score and creating one from a sample mean is that

you use the mean and standard deviation from the distribution of means.

The results of an independent-measures research study are reported as "t(18) = 2.12, p < .05, two tails." For this study, what t values formed the boundaries for the critical region?

±2.101