Exam 4: Some Key Ingredients for Inferential Statistics: the Normal Curve, Sample Versus Population, and Probability

John attained a score of 65 on his stats exam. The mean for the class was a 70 with a SD of 10. What percentage of students scored below and above John?

You wish to survey the interests of students in your statistics class. You enter the names of all students onto an Excel spreadsheet. You then use a computer program to generate a list of random names. This is called:

The __________ interpretation of probability is the understanding of probability as the proportion of a particular outcome you would obtain if you were to repeat the experiment many times.

Since 1948, all survey organizations have used the "probability method" to increase the accuracy of their results. What type of sampling method is utilized as part of this new method?

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

On a test of optimism, scores of people diagnosed with a particular disease are normally distributed with a mean of 20 and a standard deviation of 5. How high of a score does such a person with this disease need to be among the 5% most optimistic? Among the 20% most optimistic? How low of a score to be among the 10% least optimistic? Use the normal curve table and be sure to include a sketch.

The mean, standard deviation, and variance of a sample are called sample ___________.

A person received a score of 4.78 on a test. This turned out to be a Z score of +1.5. What percentage are above this score? Assume a normal distribution.

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

On a measure of writing ability, college students in general have a mean of 60, a standard deviation of 8, and the scores follow a normal distribution. a. Approximately what percentage of college students have writing ability scores above 68? Above 76? Below 52? Between 52 and 60? Use the normal curve approximation rules. b. Explain your answers and procedure to a person who is not familiar with the normal curve or normal curve areas.

A researcher wishes to conduct a survey of caregivers of Alzheimer's disease patients in the United States regarding their attitudes toward their role and the difficulties they face. What would be the best way to select the caregivers to study? Explain what a researcher would do to a person who is unfamiliar with research methods or statistics. Why might it be difficult to gather a truly random sample in this case?

The scores of the entire group of participants to which a researcher intends the results of a study to apply is called a(n)__________.

In figuring probabilities, expected relative frequency is:

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

Provide an example of a variable that is normally distributed in the general population. Why is the normal curve so common in nature?

Sixty years ago opinion polls often used the __________ method of sampling, which is now largely discredited.

You conduct a survey by giving out a questionnaire to the people you meet (and who are willing to take your questionnaire)on a given evening. You are using __________ selection.

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?

The fact that probabilities are proportions means that they:

The number of words in the active vocabulary of children of a particular age is normally distributed with a mean of 3,000 and a standard deviation of 500. a. How many words would a child of this age have to know to be in the top 2%? The top 16%? The top 50%? The bottom 2%? Use the normal curve approximation rules and include a sketch. b. Explain your answers and procedure to a person who is not familiar with the normal curve or normal curve areas.