Research Methods Test #2 Chapters 6-9

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If a hypothesis test produces a z-score in the critical region, what decision should be made?​

Reject the null hypothesis

Which of the following is a fundamental difference between the t statistic and a z-score?

The t statistic uses the sample variance in place of the population variance.

What proportion of a normal distribution is located in the tail beyond z = 1.50?​

What proportion of a normal distribution is located in the tail beyond z = 1.50?​

With α = .05, what is the critical t value for a one-tailed test with n = 15?

t = 1.761

According to the central limit theorem, the standard error for a sample mean becomes smaller as the sample size increases.​

true

Which of the following accurately describes a hypothesis test?

​An inferential technique that uses the data from a sample to draw inferences about a population

Which of the following is an accurate definition of a Type II error?

​Failing to reject a false null hypothesis

Under what circumstances will the distribution of sample means be normal?​

​If the population is normal or if the sample size is greater than 30

​What happens to the standard error of M as sample size increases?

​It decreases

What is the expected value of M?​

​The mean of the distribution of sample means

What symbol is used to identify the standard error of M?​

​σM

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?​

0.2119

What proportion of a normal distribution is located between z = 0 and z = +1.50?​

0.4332

A vertical line drawn through a normal distribution at z = 0.50 separates the distribution into two sections, the body and the tail. What proportion of the distribution is in the body?​

0.6915

A class consists of 10 male and 30 female students. If one student is randomly selected from the class, what is the probability of selecting a male student?​

10/40

For a particular population, a sample of n = 4 scores has a standard error of 6. For the same population, a sample of n = 16 scores would have a standard error of _____.​

3

If random samples, each with n = 9 scores, are selected from a normal population with µ = 80 and σ = 18, how much difference, on average, should there be between a sample mean and the population mean?

6

​Which set of characteristics will produce the smallest value for the estimated standard error?

A large sample size and a small sample variance

A normal distribution has a mean of µ = 70 with σ = 12. If one score is randomly selected from this distribution, what is the probability that the score will be less than X = 76?​

​0.6915

Which combination of factors will produce the largest value for the standard error?​

​A small sample and a large standard deviation

The critical boundaries for a hypothesis test are z = +1.96 and − 1.96. If the z-score for the sample data is z = − 1.90, what is the correct statistical decision?​

​Fail to reject H0

​When n is small (less than 30), how does the shape of the t distribution compare to the normal distribution?

​It is flatter and more spread out than the normal distribution.

​Which of the following describes what a confidence interval does?

​It uses a sample mean to estimate the corresponding population mean.

Which of the following accurately describes the critical region?​

​Outcomes with a very low probability if the null hypothesis is true

Which of the following is an accurate definition of a Type I error?​

​Rejecting a true null hypothesis

What is the standard error of M?​

​The standard deviation of the distribution of sample means

​Which of the following will increase the power of a statistical test?

​The treatment has no effect on the scores.

With α = .05, how are the boundaries for the critical region determined?​

Boundaries are drawn so there is 2.5% (.025) in each tail of the distribution.

IQ scores form a normal distribution with µ = 100 and σ = 15. Individuals with IQs above 140 are classified in the genius category. What proportion of the population consists of geniuses?​

0.0038

What proportion of a normal distribution is located between the mean and z = 1.40

0.4192

What proportion of a normal distribution is located between z = -1.25 and z = +1.25?​

0.7888

The results of a hypothesis test are reported as follows: t(15) = 2.70, p < .05. Based on this report, how many individuals were in the sample?​

16

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

20

​Under what circumstances can a very small treatment effect be statistically significant?

If the sample size big and the sample variance is small

​A sample of n = 25 scores produces a t statistic of t = 2.062. If the researcher is using a two-tailed test, which of the following is the correct statistical decision?

The researcher must fail to reject the null hypothesis with either α = .05 or α = .01.

You complete a hypothesis test using α = .05, and based on the evidence from the sample, your decision is to reject the null hypothesis. Which of the following is true?​

You might have made a Type I error, but the probability is less than 5%.

Which of the following is a requirement for a random sample?​ Every individual has an equal chance of being selected. 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. all answers are correct

​What happens to the expected value of M as sample size increases?

it stays constant

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

t=0


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