STAT 401 Lab Activity #1
24 Jan 2007
Objective : To implement simple random sampling from finite population in MINITAB.
To verify sampling variability of the sample mean/proportion.
Part I. (Similar to homework problem 3)
In the Macworld Conference & Expo Keynote Address on 01/09/2007 Steve Jobs
announced a new product, the iPhone. Suppose we want to select 15 devices, from the
pilot lot of 70 iPhones, to inspect feature coordination. Describe
1) In the Minitab Worksheet create a column (C1) of numbers from 1 to 70, those
numbers will be the ID’s of the devices from the pilot lot.
Calc > Make Patterned Data > Simple Set of Numbers
Enter C1 in "Store patterned data in:", Enter 1 in "From first value:____",
Enter 70 in "To last value:_____", Enter 1 in "In steps of: ____",
Enter 1 in "List each value ______ times".
Enter 1 in "List the whole sequence ______ times". Click OK.
2) In the menu select the dialog window:
Calc > Random Data > Sample From Columns
In the dialog window specify that you want to sample 17 rows from column C1
and store the sample in column C2.
3) Record the obtained sample here:
Part II. (Similar to homework problem 11.)
A car manufacturer receives a shipment of N = 10, 000 navigation systems that are to be
installed as a standard features in the next line of luxury cars. Of concern is a type of
satellite reception malfunction. Suppose N1 = 100 systems have this malfunction
(category 1) and N2 = 9, 900 do not (category 2). We want to draw a simple random
sample of 1000, and calculate the sample proportion of defective systems.
1) Let 1 denote category 1, and 0 denote category 2. Create the statistical population
in a Minitab column using the following sets of commands:
Calc > Make Patterned Data > Simple Set of Numbers
Enter C1 in "Store patterned data in:", Enter 1 in "From first value:____",
Enter 1 in "To last value:_____", Enter 1 in "In steps of: ____",
Enter 100 in "List each value ______ times".
Enter 1 in "List the whole sequence ______ times". Click OK.
Using similar set of commands enter 0 in the first 9900 rows of column 2.
Next, stack two columns to get the statistical population in column 3 :
Data > Stack > Columns
Enter C1 C2 in "Stack the following columns:", Check "Column of current
worksheet" and enter C3, click OK.
2) Let’s draw a simple random sample of size 1000 from the statistical population
using the commands given in Problem I.
3) Calculate the sample proportion of systems with reception malfunction (coded 1),
using the commands:
Calc > Column Statistics
Select "Mean", Enter C4 in "Input Variable", click OK.
Use commands in step (3) to calculate the population proportion of the units with
reception malfunction. Since our statistical population is stored in column 3 you need to
enter C3 as an input variable. (Note that in order to calculate the proportions we selected
the option “Mean”, as discussed in class.)
Part III. Simulating rolls of a die. Checking that the “relative frequencies” approximate
probabilities
1) Enter the numbers 1,...,6 in a column c4 and sample with replacement 100 times.
2) Use the commands:
Stat>Basic Statistics>Display Discriptive Statistics>Enter c4 in “Variables” and
in “By variables (optional)”, Click on Statistics and select “N total” “Percent”,
“Cumulative percent”. OK, OK
This will give the frequencies and relative frequencies that each of the numbers 1,…,6
was selected. Compare with the probability of 1/6=0.1667.
Repeat the above with a sample of size 1,000 die rolls.