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Chapter 4: Q. 19 (page 238)

SRS of engineers? A corporation employs 2000 male and 500 female engineers. A stratified random sample of 200 male and 50 female engineers gives every individual in the population the same chance to be chosen for the sample. Is it an SRS? Explain your answer.

Short Answer

Expert verified

It is not an SRS as some samples have no chance of being selected.

Step by step solution

01

Given information

We need o find whether the given data is SRS or not

02

Explanation

A sample of size nis used in simple random sampling, and each sample of size nhas an equal probability of being chosen.

In this example, the sample will include 200male engineers and 50female engineers chosen randomly.

This sample, however, will not be a simple random sample, as some samples will have no probability of being chosen (for example, a sample of 250guys), while others will have a possibility of being chosen.

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Most popular questions from this chapter

Suppose that 35% of the voters in a state are registered as Republicans, 40% as

Democrats, and 25% as Independents. A newspaper wants to select a sample of 1000

registered voters to predict the outcome of the next election. If it randomly selects 350

Republicans, randomly selects 400 Democrats, and randomly selects 250 Independents,

did this sampling procedure result in a simple random sample of registered voters from

this state?

a. Yes, because each registered voter had the same chance of being chosen.

b. Yes, because random chance was involved.

c. No, because not all registered voters had the same chance of being chosen.

d. No, because a different number of registered voters was selected from each party.

e. No, because not all possible groups of 1000 registered voters had the same chance of

being chosen.

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Oils and inflammation The extracts of avocado and soybean oils have been shown to slow cell inflammation in test tubes. Will taking avocado and soybean unsaponifiables (called ASU) help relieve pain for subjects with joint stiffness due to arthritis? In an experiment, 345 men and women were randomly assigned to receive either

300 milligrams of ASU daily for three years or a placebo daily for three years.

Explain why it was necessary to include a control group in this experiment.

SRS of students? At a party, there are 30 students over age 21 and 20students underage21. You choose at random 3 of those over 21 and separately choose at random 2 of those under 21 to interview about their attitudes toward alcohol. You have given every student at the party the same chance to be interviewed. Is your sample an SRS? Explain your answer.

I work out a lot Are people influenced by what others say? Michael conducted an experiment in front of a popular gym. As people entered, he asked them how many days they typically work out per week. As he asked the question, he showed the subjects one of two clipboards, determined at random. Clipboard A had the question and many responses written down, where the majority of responses were6or7days per week. Clipboard B was the same, except most of the responses were1or2days per week. The mean response for the Clipboard A group was4.68and the mean response for the Clipboard B group was4.21.

a. Calculate the difference (Clipboard A – Clipboard B) in the mean number of days for the two groups. One hundred trials of a simulation were performed to see what differences in means would occur due only to chance variation in the random assignment, assuming that the responses on the clipboard don’t matter. The results are shown in the dotplot.

b. There is one dot at0.72. Explain what this dot means in this context.

c. Use the results of the simulation to determine if the difference in means from part (a) is statistically significant. Explain your reasoning.
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