Exam 1: Introduction to Statistics

Identify which of these types of sampling is used: random, stratified, systematic, cluster, convenience. -49, 34, and 48 students are selected from the Sophomore, Junior, and Senior classes with 496, 348, and 481 students respectively.

In a cross-sectional study, data are ________.

The sample of spheres categorized from softest to hardest.

"38% of adults in the United States regularly visit a doctor". This conclusion was reached by a college student after she had questioned 520 randomly selected members of her college. What is wrong with her survey?

Identify which type of sampling is used. The name of each contestant is written on a separate card, the cards are placed in a bag, and three names are picked from the bag.

A study of achievement scores by sixth-grade students on a standardized math test showed the three top scorers were all gifted piano players. Conclusion: Playing the piano leads to mathematical achievement.

Provide an appropriate response. -A researcher obtains an alphabetical list of the 2560 students at a college. She uses a random number generator to obtain 50 numbers between 1 and 2560. She chooses the 50 students corresponding to those numbers. Does This sampling plan result in a random sample? Simple random sample? Explain.

Survey responses of "good, better, best".

Ages of survey respondents.

Identify the type of observational study (cross-sectional, retrospective, prospective). -A market researcher obtains a sample of 50 people by standing outside a store and asking every 20th person who enters the store to fill out a survey until she has 50 people. What sampling method is being used here? Will the resulting sample be a random sample? Will it be a simple random sample? Explain your thinking.

Temperatures of the ocean at various depths.

Identify the type of observational study (cross-sectional, retrospective, prospective). -Researchers collect data by interviewing athletes who have won olympic gold medals from 1992 to 2008.

At a school there are two different math classes for children of the same age. The two classes have different teachers. The school principal is interested in gauging the effectiveness of two different teaching methods and asks each teacher to try one of the methods. At the end of the semester both classes are given the same test and the results are compared. In this experiment, what is the variable of interest? Give some examples of variables which could be confounding variables.

Jon consulted with an accountant to prepare his tax return. He recommended the accountant to his friend saying that this year the amount he paid in taxes was 150% less than last year. What is wrong with this statement?

A coach uses a new technique in training middle distance runners. The times, in seconds, for 8 different athletes to run 800 meters before and after this training are shown below. Athlete Before 115.2 114 116.4 119.8 110.9 112.4 111.5 117.3 After 112.9 112.7 114 120.6 109.1 107.9 113.4 Does the conclusion that the technique is effective appear to be supported with statistical significance? Does the conclusion that the technique is effective appear to have practical significance?

Identify the type of observational study (cross-sectional, retrospective, prospective). -Why do you think that cluster sampling is frequently used in practice.

Amount of fat (in grams) in cookies.

Identify the sample and population. Also, determine whether the sample is likely to be representative of the population. A study is interested in whether men and women are equally likely to vote Democratic, Republican or Independent or not vote in a presidential election. Results were polled through a popular news website.

Student's grades, A, B, or C, on a test.

Identify the type of observational study used. A town obtains current employment data by polling 10,000 of its citizens this month.