Psych Statistics - Module 2 Test

A person received a test score that is in the top 32% and the test scores follow a normal curve. This person's Z score must be at least:

.46

What IQ score would a person need to be in the top 5% of the general population? Assume M = 100 and SD = 16.

115.44 OR 126.24 (unconfirmed) (other options 110.45/120.05 are incorrect)

In a housing project there are 350 households in which English is usually spoken, 50 in which Spanish is usually spoken, and 100 in which the language is other than English or Spanish. A researcher approaches a house at random to conduct an interview. What is the chance that the usual language in that household will NOT be English?

150/500 = .3

If a person has an IQ of 130, approximately what percentage of people have higher IQs? Assume M = 100 and SD = 16.

3%

Place the five steps of the hypothesis-testing process in the correct order: 1.Determine the characteristics of the comparison distribution. 2.Decide whether to reject the null hypothesis. 3.Restate the question as a research hypothesis and a null hypothesis about the populations. 4.Determine your sample's score on the comparison distribution. 5.Determine the cutoff sample score on the comparison distribution at which the null hypothesis should be rejected.

3, 1, 5, 4, 2

On a normal curve, what percentage of scores fall between a Z score of 1.29 and a Z score of 1.49?

3.04

If you were to select a score at random from a distribution that follows a normal curve, what approximately is the probability of selecting a score between Z scores of 0 and +1?

34%

The mean score on a creativity test is 20 and the standard deviation is 5. The distribution is normal. Using the percentage approximations for the normal curve, how many people would attain a score between 15 and 25?

34% + 34% = 68%

What Z score would a person need to be in the top 4% of his or her class on a particular test? Assume a normal distribution.

50% - 4% = 46%, which corresponds to a Z score of 1.75

A particular nation has a human rights score of 41, which equals a Z score of 1.3. What is the percentage of nations above this score? (Assume a normal distribution.)

50% - 40.32% = 9.68%

Carrie attained a score of 650 on the verbal section of her SAT. The mean grade was a 500 with a standard deviation of 100. What percentage of test takers scored below and above Carrie?

93 and 7

A researcher conducts extensive interviews with 40 workers at a large factory in order to examine the morale among workers in general at that factory. In this example, what is the population?

All the workers in the factory

How do you determine whether or not to reject the null hypothesis?

Compare the Z score needed to reject the null hypothesis to the actual sample Z score

You determine the characteristics of the comparison distribution to answer which of the following questions?

Given a particular sample value, what is the probability of obtaining that value if the null hypothesis is true?

What is a correct argument for using a two-tailed test even if there is a clear basis for predicting a result in a given direction?

If an unexpected result comes out opposite to what is predicted, it does not have to be ignored.

A researcher tests whether a new teaching method is more effective than the old one. What is the RESEARCH hypothesis?

The new teaching method is more effective than the old teaching method.

A researcher tests whether there is any difference between how fast people work in the morning versus how fast they work in the evening. What is the NULL hypothesis?

There is no difference in the speed at which people work.

You want to know if a new employee incentive program really works. How would you test the hypothesis that it does work?

Try to disprove the hypothesis that it does not work

Suppose that a researcher wants to know if a new flu drug affects people, either by making them better or worse. Would this be a one-tailed or two-tailed test and why?

Two-tailed because there is no predicted direction of the effect of the drug

Suppose you conduct a study in which you set the significance level cutoff at a lenient probability level, such as 15%. In this case, you would have a 15% chance of making a:

Type I error

If you were looking at a graph of a normal distribution, which of the following would best describe it?

Unimodal, roughly symmetrical, and bell-shaped

Failing to reject the null hypothesis when the research hypothesis is true is referred to as:

a Type II error

Setting the significance level at a very extreme cutoff (such as .001) increases the chances of:

a Type II error

The fact that probabilities are proportions means that they:

can't be lower than zero or more than one

If you want to know something about a population, your results would be MOST accurate if you could study the:

entire population

A researcher wants to know if a new type of health insurance works better or worse than a standard form of health insurance. The hypothesis that there will be no difference between the new type of insurance and the old type of insurance is called the:

null hypothesis

In most behavioral and social science research articles, unless the researcher specifically states that a __________ test was used, it is assumed that it was a __________.

one-tailed; two-tailed

Based on the results of his study, a researcher rejects the null hypothesis because the probability of obtaining his result if the null hypothesis were true is less than 5%. How would this be symbolized?

p < .05

In statistics writing, it is common to use Greek letters for:

population parameters

Decision errors are possible in hypothesis testing because you are making decisions about _______ based on information in ________.

populations; samples

You have an aquarium full of tropical salt-water fish and you need to know the exact salt content of the water. To test it, you take a cup and scoop some of the water out. In statistical language, the scoop of water is a:

sample

If the null hypothesis is rejected, the researcher can conclude that the results:

support the research hypothesis OR prove that the research hypothesis is true (unconfirmed which is correct yet)

The cutoff Z score on the comparison distribution is 1.64 and the sample value has a score of 1.32 on the comparison distribution.

the null hypothesis cannot be rejected

A sample is studied to see if it represents a population (called Population 1) that is different from a known population (called Population 2). The comparison distribution is:

the same as the distribution of Population 2