Math 503

Lab: Probability, Tables, and Sampling

Load the Pulse data set that is located on L:\MTBWin\data\pulse into Minitab

Part I: Probability and Tables

A student is selected at random from this group of 92 students.

1. What is the probability this student is male?

2. What is the probability this student is a smoker?

3. What is the probability this student is a female smoker?

4. Someone tells you this student is female. What is the probability this student smokes?

5. Someone tells you this student is a smoker. What is the probability this student is female?

6. What is the probability this student is male or this student is a smoker?

To answer these questions more easily, use Mintab to make a two by two table with rows corresponding to gender and columns corresponding to smoking. To do this.

Label columns C9 and C10 Gender and Smoker

Use Manip, Code, Numeric to Text

Put Sex in the Code Data from Columns window

Put Gender into the into Columns window

Put 1 and 2 into the Original Values windows

Put Male and Female into the corresponding New windows

Click Ok

Do the same thing with Smokes and Smokers, coding 1 as a Yes and 2 as a No.

Use Stat, Tables, Cross Tabulation ...

Put Smoker and Gender in the Classification variables window

Make sure just the Counts box is checked

Click Ok

Now you should be able to use the table in the session window to answer the questions.

Do you think the table suggests there is a relationship between gender and smoking? Suppose there were no relationship between gender and smoking and suppose you knew the row and column totals. What number would you expect to see in the cells? It may help to see Minitab=s answer to this question. To see it

Use Stat, Tables, Cross Tabulation ...

Uncheck the Counts box

Check Chi-Square Analysis

Click on the button Above and Expected Count.

Click Ok

Part II: Probability and Sampling

How likely it is that a sample mean will be close to a population mean? To begin

Use Stat, Basic Statistics, Display Descriptive Statistics to find the mean height of the 92.

Next select a random sample of size 10 from these 92 students and compute the mean of the sample.

To select a random sample

Label C11 SampleHeight

Use Calc, Random Data, Sample from Columns

Put 10 in the Sample window

Put Height in the Rows from Columns window

Put SampleHeight in the Store Samples In window

Click Ok

Find the mean of this sample

Repeat this sampling 10 times or more times, keeping track of the sample means that you get.

What can you say about this new data set of sample means? Hint: Look at the mean of these and a histogram or stem-and-leaf plot. You may want to work together.

Repeat the entire process (Part II) using samples of size 50.