extra credit - sya4400

An independent-sample study has one sample with n = 10 and a second sample with n = 15 to compare two experimental treatments. What is the df value for the t statistic for this study?

a. 23 b. 24

uestion 3 What is the value of the median for the following set of scores? Scores: 1, 3, 4, 6, 7, 8, 12, 2

a. 6.5 c. 7

A hypothesis test and estimation can both be used to address a question about a treatment effect. What question is addressed by each?

a. The hypothesis test asks whether there is any effect and estimation asks how much. d. Both ask how much effect the treatment has.

If other factors are held constant, what happens to a confidence interval if the size of the sample increases?

a. The standard error decreases and the width of the interval decreases. c. The standard error increases and the width of the interval decreases.

If you fail to reject the null hypothesis in independent sample t tests, you are concluding that _______.

a. Two populations have a same mean. d. Two samples have different means.

Which statistical techniques can be used to predict a value in one variable from a value in another variable?

a. correlation b. regression

In the general linear equation, Y = bX + a, what is the value of b called?

a. slope c. Y intercept

Because independent sample t tests involve variances from two samples, _______.

a. you take a difference between the sample variances. b. you add the sample variances. d. you pool the variances.

In a distribution, the "body" proportion is larger than the tail.

a. * always true

A Pearson correlation of r = +0.85 indicates that a graph of the data would show:

a. * points clustered close to a line that slopes up to the right.

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

a. * µ1 - µ2 = 0

What position in the distribution corresponds to a z-score of z = +2.00?

b. Below the mean by a distance equal to 2 standard deviations. c. Above the mean by a distance equal to 2 standard deviations.

Using a sample of Florida residents, a 95% confidence interval for personal income was constructed. Which of the following statement is true?

b. The interval has a 95% chance of including population mean. c. The interval has a 95% chance of rejecting the null hypothesis.

A random sample of n = 36 scores is selected from a population. Which of the following distributions definitely will be normal?

b. The scores in the population will form a normal distribution. c. The distribution of sample means will form a normal distribution.

The critical region consists of sample means that are __________ to be observed when the null hypothesis is true.

b. unlikely

In an introductory psychology class with n = 50 students, there are 9 freshman males, 15 freshman females, 8 sophomore males, 12 sophomore females, and 6 junior females. If one student is randomly selected from this class, what is the probability of getting a sophomore?

b. * 20/50

Z-scores are "standardized" in a sense that they are always expressed in the unit of...

b. * Standard deviation

What is measured by the estimated standard error, sM?

b. * The average distance between a sample mean and the population mean.

To compute a t statistic, you must know ________.

b. * estimated standard error

Because independent sample t tests involve two unknown population means, _______.

b. * **??? you test null and alternative hypotheses about the population mean difference.

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

b. * ???? Failing to reject a false null hypothesis.

A professor recorded the academic major for each student in an introductory psychology class. If the data are presented in a frequency distribution graph, what type of graph should be used?

c. either a histogram or a polygon d. a bar graph

The students in a psychology class seemed to think that the midterm exam was very easy. If they are correct, what is the most likely shape for the distribution of exam scores?

c. * negatively skewed

Suppose the correlation between height and weight for adults is +0.80. What proportion (or percent) of the variability in weight can be explained by the relationship with height?

c. * 64%

In hypothesis testing, you use _____ data to test hypotheses about an unknown ______ mean.

c. * sample, population

A researcher is conducting an experiment to evaluate a treatment that is expected to increase the scores for individuals in a population which is known to have a mean of µ = 80. The results will be examined using a one-tailed hypothesis test. Which of the following is the correct statement of the null hypothesis?

c. * ??? µ ≤ 80

Which of the following is a difference between a hypothesis test with the t statistic and a test with a z-score?

d. * All of the other options are differences.

True or false? If the sample size is increased, then the standard error for sample means will also increase. a. True. b. False.

false

To calculate the variance for a sample, SS is divided by n -1, instead of n.

true

True or false? If the highest score in a distribution is X = 16 and the lowest is X = 4, then the range is 12 or 13 points.

true