Statistics for Behavioral Sciences - Midterm Exam

For a population with µ = 84 and σ = 4, what is the z-score corresponding to X = 80?

-1.00

Using the frequency distribution table below, what is the proportion of individuals that scored a 4? X f 6 4 5 3 4 7 3 2 2 2 1 2

.35

For any distribution, what is the z-score corresponding to the mean?

0

All the possible samples of n = 4 scores are selected from a population with µ = 20. If the average for all of the sample means is calculated, which value will be obtained?

20

For an exam with a mean of M = 74 and a standard deviation of s = 8, Mary has a score of X = 80, Bob's score corresponds to z = +1.50, and Sue's score is located above the mean by 10 points. If the students are placed in order from smallest score to largest exam score, what is the correct order?

Mary, Sue, Bob

Which symbol below identifies the sample variance?

s2

What is the mode for the population of scores shown in the frequency distribution table? X f 5 3 4 4 3 3 2 3 1 2

4

If the mean on an intelligence test is 100, what score indicates an excellent score?

145

For the following distribution of quiz scores, if a score of X = 4 or lower is a failing grade, how many individuals failed the quiz? X f 6 3 5 6 4 5 3 5 2 3 1 2

15

What is the total number of scores for the distribution shown in the following table? X f 4 7 3 5 2 4 1 2

18

A sample of n = 15 scores has M = 20 and s2 = 9. What is the sample standard deviation?

3

A sample of n = 6 scores has SS = 40. If these same scores were a population, then the SS for the population would be _____.

40.

What is the value of ΣX2 for the scores 2, 4, and 5?

45

What the variance for the following sample of n = 3 scores? Scores: 1, 4, 7

9

Consider the distribution of exam scores for the first exam within a college course. If the set of exam scores forms a symmetrical distribution, what can be concluded about the students' scores?

About an equal number of students had relatively high and relatively low scores.

Which of the following is true for most distributions?

Around 70% of the scores will be located within one standard deviation of the mean.

Which of the following statements about the comparison between effect size and power is correct?

As effect size increases, power also increases.

If α = .05 for a two-tailed hypothesis test, how are the boundaries for the critical region determined?

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

For the following grouped frequency distribution table of exam scores, what is the lowest score on the exam? X f 90-99 3 80-89 1 70-79 2 60-69 3 50-59 4

Cannot be determined

Which statement below is true?

It is possible for a distribution of scores to have two modes.

What is the mean from the list of scores below: 2 2 2

M = 2

Which of the following is not an underlying assumption of hypothesis testing in the context of a research study?

The sample size must be greater than n = 30.

Which of the following accurately describes a hypothesis test?

a statistical technique that uses the data from a sample to evaluate a hypothesis about a population. Must be testable.

A large z indicates...

an extreme score.

A researcher is interested in having as much ability as possible to identify a treatment effect if one really exists. Which of the following strategies should they employ?

change the sample size from n = 25 to n = 100

Which of the following actions will always change the value of the mean?

changing the value of one score

A researcher is interested in whether a new reading technique influences the reading ability of elementary school children. The researcher knows that average reading ability among a population of third graders is µ = 3 with a standard deviation of σ = 1. If the researcher administers the new reading technique to a third grader who subsequently scores X = 4, it can be concluded that the new reading technique _____.

does not have an influence on reading ability.

In order for a researcher to obtain a random sample, they need to specifically do which of the following things?

ensure that each person in the population has an equal chance of being selected for the sample

Because sample variances are computed by dividing SS by n - 1, the average value of the sample variances from all possible random samples consistently _____ the population variance.

equal

Even if a treatment has an effect, it is still possible to obtain a sample mean after the treatment that is very similar to the original population mean. Which outcome is likely if this happens?

fail to reject H0 and make a Type II error

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

failing to reject a false null hypothesis

The Null hypothesis (H0) states that the treatment has

no effect

A researcher tests their new treatment for sleep disorder among an individual that has a sleep disorder. The researcher knows that individuals diagnosed with sleep disorder tend to have sleep quality scores that form a normal distribution with µ = 40 and σ = 6. The researcher finds that this individual has a sleep quality score of X = 53 following treatment. Which is the probability that a score this large or larger would be obtained if the new treatment had no effect?

p = 0.0150

What is the shape of the distribution for the following set of data? Scores: 1, 1, 1, 1, 1, 2, 2, 2, 3, 3, 4, 5

positively skewed

What is the shape of the frequency distribution for the following set of data regarding students' scores on a 10-item quiz? X f 9 1 8 1 7 3 6 6 5 6

positively skewed

What scale of measurement is being used when a researcher measures the amount of car accidents that participants have been involved in during their lifetime?

ratio

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

reject the null hypothesis

A researcher conducts a hypothesis test to evaluate the effect of a treatment that is expected to increase scores. The hypothesis test produces a z-score of z = +2.27. If the researcher is using a one-tailed test, which is the correct statistical decision?

reject the null hypothesis with α = .05 but not with α = .01

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

rejecting a true null hypothesis

A hypothesis test involves a comparison of which two elements?

research results from a sample and a hypothesis about a population

A population of N = 5 scores has a variance of σ2 = 24. If the scores were from a sample, what value would be obtained for the sample variance?

s2 = 30

Which of the following accurately describes the critical region?

sample means that are very unlikely to be obtained if the null hypothesis is true

Consider a researcher who is exploring new potential treatments for specific forms of cancer. This researcher is extremely focused on avoiding mistakes in concluding that treatments that may very well be effective are ineffective when conducting their research. What should this researcher do?

set a higher alpha level

Keith conducts a research study to examine how mental fatigue influences frustration levels. He has one group of participants complete a mentally exhausting problem-solving task for ten minutes, and a second group of participants complete an easy crossword puzzle for ten minutes. Then, he observes participant reactions to being prevented from achieving a desired goal on a second unrelated task as a measure of frustration levels. In this research study, the experimental condition is _____.

the group of participants who complete the mentally exhausting problem-solving task.

At an organization, scoring in the middle 80% of employees regarding job performance is designated as satisfactory. Job performance is a normally distributed variable. Individuals designated as having satisfactory job performance would have job performance scores that correspond with z-scores equal to or between _____.

z = -1.28 and z = +1.28

A population has µ = 30 and σ = 10. If 5 points are added to every score in the population, what are the new values for the mean and standard deviation?

µ = 35 and σ = 10

In a population with σ = 5, a score of X = 46 corresponds to a z-score of z = +0.40. What is the population mean?

µ = 44

A population has µ = 50. Which value of σ would make X = 55 an extreme value out in the tail of the population distribution?

σ = 1