STAT 301 - Business Statistics
Lecture Review #6 - Standard Deviation

Review questions:

1) What is the variance? The standard deviation?

2) Why does the sample variance and standard deviation divide by n-1 rather than n?

3) For normal data, what percentage of the data lie within one standard deviation of the mean? Two standard deviations? Three standard deviations?

Computational exercises:

1) You should be able to compute, by hand, basic statistics covered in this class, for "nice" data sets (small sets of integers with integer means). This shows basic understanding of the procedure and its underlying concepts. Find the (sample) standard deviation for each of the following sets of data. Show your work.

a) 3, 7, 2, 4

b) 6, 8, 4

c) 861934284296, 861934284298, 861934284294

2) Back in the Dark Ages (before calculators and computers were widespread) an important part of any applied statistics course was figuring out how to do computations, in a manageable way, with real data. Perhaps a third of the textbook might be devoted to developing computational shortcuts and tricks. Nowadays we just have the machine do the dirty work for us. (Be very grateful!) You should know how to use computer tools to analyze real data.

The data set NORMTEMP.xlsx gives data on measured body temperatures from a sample of 130 individuals (65 men and 65 women). For these data, find the (sample) mean and standard deviation body temperature for the men, and for the women. Just glancing at these numbers (without doing any further analysis), does it appear that there is a difference between the two groups?

SOLUTIONS:
1a) 2.16
1b) 2
1c) 2
2) men: 98.105, 0.699
    women: 98.394, 0.743