PSY-380 Exam 2

Researchers record the number of errors on some behavioral task for 15 participants. They report a sample mean equal to 6 ± 1 (M ± SD). What is the critical value for a two-tailed test with α = .01?

+- 2.997

The criterion or level of significance in behavioral research is typically set at what probability value?

0.05

State the Four Steps of Hypothesis Testing

1. State the Hypothesis 2. Set the Criteria 3. Compute the Test Statistic 4. Make a Decision

A researcher selects a sample of 49 students to test the null hypothesis that the average student exercises 90 minutes per week. What is the mean for the sampling distribution for this population of interest if the null hypothesis is true?

2.90 minutes per week

How does increasing sample size affect the estimate of the population variance?

As sample size increases, the sample variance more closely approximates the population variance

The __________________ is a normal-like distribution with greater variability in the tails than a normal distribution because the sample variance is substituted for the population variance to estimate the standard error in this distribution.

Distribution

________ measures the size of an effect in a population, whereas ______________ measures whether an effect exists in a population.

Effect size, hypothesis testing

Why do we find the difference between pairs of scores (compute difference scores) before computing the test statistic for a related-samples t test?

Eliminates the between-persons error

What value is placed in the denominator of the test statistic for the related-samples t test?

Estimated Standard Error for difference scores

True or False: Researchers select a sample from a population to learn more about characteristics in that sample

False: sample from a population to learn more about the population

When a population is associated with a small effect size, what can a researcher do to increase the power of the study?

Increase the sample size

A researcher records the amount of computer use (in hours per day) in a sample of students and then matches the students based on their amount of computer use. Is this an example of matching through experimental manipulation or matching through natural occurrence?

Matching through experimental manipulation

Is the following set of hypotheses appropriate for a directional or a nondirectional hypothesis test? H0: μ = 35 H1: μ ≠ 35

Nondirectional

What are the assumptions for a related-samples t test?

Normality and independence

What are three assumptions of the one-sample t test?

Normality, random sampling, and independence

What are the four assumptions for the two-independent-sample t test?

Normality, random sampling, independence, equal variance

The decision in hypothesis testing is to retain or reject which hypothesis?

Null Hypothesis

What measure, eta-squared or omega-squared, gives a more conservative or smaller estimate of proportion of variance?

Omega-squared

Which type of test, one-tailed or two-tailed, is susceptible to the possibility of committing a Type III error?

One-tailed test

Distinguish between the repeated-measures design and the matched-pairs design.

Participants are observed more than once in repeated-matched design but matched-pairs participants are observed once

As effect size decreases, what happens to power?

Power decreases

As effect size increases, what happens to power?

Power increases

State the two correct decisions that a researcher can make.

RETAIN or REJECT the null hypothesis

A researcher conducts a hypothesis test and finds that p = .0689. What is the decision for a hypothesis test at a .05 level of significance?

Reject the null hypothesis

A researcher conducts a one-sample z test. The z statistic for the upper-tail critical test at a .05 level of significance is zobt = 1.84. What is the decision for this test?

Reject the null hypothesis

A test statistic is associated with a p value less than .05. What is the decision for this hypothesis test?

Reject the null hypothesis

An estimated Cohen's d substitutes which value in the formula to estimate the population standard deviation?

Sample standard deviation

On average, what do we expect the sample mean to be?

The Population Mean

What is the denominator for the estimated Cohen's d when used with the related-samples t test?

The Standard deviation of the difference scores

True or False: the effect size, power, and sample size of a study can affect the decisions we make in hypothesis testing

True

True or false: The related-samples t test can be used for the repeated-measures design and the matched-pairs design.

True

What type of error do we directly control?

Type 1 Error

What type of error is associated with decisions to reject the null hypothesis?

Type 1 Error

What type of error is associated with decisions to retain the null hypothesis?

Type 2 Error

If the null hypothesis is rejected, did we reach significance?

Yes

Assuming α = .05, what is the critical value in each of the following t distributions? (a) df = 10, two-tailed test (b) df = 30, one-tailed test (lower tail critical) (c) df = ∞, two-tailed test (d) df = 15, one-tailed test (upper tail critical)

a) 2.228 b) 1.697 c) 1.96 d)1.753

For the following statements, write increases or decreases as an answer. The likelihood that we reject the null hypothesis (increases or decreases): (a) The closer the value of a sample mean is to the value stated by the null hypothesis. (b) The further the value of a sample mean is from the value stated in the null hypothesis.

a) Decreases b) increases

A researcher compares the mean grade point average (GPA) of college students with a full-time job to the mean GPA of the general population of college students. In this example, identify (a) the dependent variable and (b) the treatment.

a) GPA b) having a full time job

State whether each of the following values for estimated Cohen's d has a small, medium, or large effect size. (a) 0.40 (b) 1.20 (c) 0.05 (d) 0.10

a) medium b) large c) small d) small

How does computing difference scores increase the power of a related-samples t test compared to a two independent- sample t test?

eliminates between person error, reducing the estimate for standard error in the denominator

What value is placed in the denominator for the two-independent-sample t test?

estimated standard error

What is the main limitation of the z test in behavioral research?

it requires that the population variance is know, and this is rarely known in behavioral research

What is the calculation for the degrees of freedom of a t distribution?

n-1

Name two types of repeated-measures designs.

pre-post design within subject design

How do related samples differ from independent samples?

related samples participants are related, measured more than one and matched on common traits independents samples participants are not related because different participants are observed in each group