Assignment 4

Name___________________________

(Printed)

Student Number___________________

(Social Security Number)

E-mail__________________________

1. Samples and Populations
1. Retrieve the data set "Phones" from the web site.
1. This file consists of a single variable, percent of housing units without telephones for all counties in the United States. We will treat these data as a population.
2. The batch size is 3,141. This file will "fit" in the student version but with not a lot of room to spare. So don't try adding extra variables and so forth.
3. You then draw a sample from the population by using MINITAB or SPSS's random sampling procedures.
2. Read the data into say column 1 with the usual methods. That is, download the file under a name such as phones.dat.
1. If you are using the student version of MINITAB, go to File, then Import Ascii data. In the dialogue box type c1 and press OK. In the next box located the directory and file that contains phone.dat, and click OK.
2. For the full version (Version 10 or 11) use File and then Other files. Choose Import special text. In the dialogue box type c1 and click OK. Then locate the file and click OK.
3. Now, draw a random sample of 50 counties:
1. For both versions use Calc and then Random Data. Click on Sample from columns.
2. Fill in the dialogue box, the entries of which are more or less self-explanatory. In the Sample box type 50. Then type c1 in the from column(s) box. Finally, store the samples in c2 or sample50.
3. In essence you are drawing a random sample of 50 counties and storing the observations in column two, which can be named sample50.
4. You can now compare sample statistics with corresponding population values.
4. Draw a stem-and-leaf display and attach.
1. Note: use at least two stems for each digit (e.g., 0., 0* or 0., 0T, 0F, 0S, 0*).
5. Draw a box-and-whisker plot and attach.
6. Obtain these statistics:

1. Your estimates should be relatively close to the corresponding population values. But in all likelihood they will not match exactly. Note: sample values will of course vary from person to person.
1. What happens when the sample size is increased?
1. Repeat step C-ii above but draw samples of size 10, 20, 100, and 300.
2. Find these statistics for the samples and the population.

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