## Sunday, November 14, 2010

### Chapter 8.13

Chapter 8.13

Note that the sample size is only 8 and you don’t know whether the population from which the sample is drawn is normally distributed or not. In this situation use the t distribution. Put the numbers into Excel and then find the margin of error using the t distribution.....go to data analysis> descriptive stats and it is the number at the bottom of the table.

My results are:

Column1

Mean 10
Standard Error 1.224745
Median 10.5
Mode #N/A
Standard Deviation 3.464102
Sample Variance 12
Kurtosis -1.04286
Skewness -0.16496
Range 10
Minimum 5
Maximum 15
Sum 80
Count 8
Confidence Level(95.0%) 2.896061

So for 13 (a) xbar is 10; for (b) 3.464, and (c) is 2.896. The last question is the Confidence Interval. That’s easy: 10 – 2.896 and 10 + 2.896....note you MUST actually finish off this little calculation.

Difference between cluster sampling and stratified: think of cluster being used for spatial problems, such as the example about trees with beetles in BC. Stratified is used when we can easily divide the population into homogeneous groups, for example golf-club membership