Elementary Survey Sampling 7th Edition Sampling from Real Po

Elementary Survey Sampling 7th Edition

Sampling from Real Populations 11.4

Estimate the average number of words per page among pages that contain no boxed formulas or tables in this book.

Solution

To estimate the number of words in the pages that contain no boxed formula of tables, you will have to follow the steps of standard sampling

First you need to select randomly a sample of 30 pages that contain no tables or boxed formula. Remember that a size of 30 is recommended so that the central limit theorem is valid and we can then estimate the population parameter confidence interval.

If you take a sample of size smaller than 30, you will have to assume that the number of words in such pages is normally distributed.

Once you have chosen the type of sampling, count the number of words in each page and note it down as sample data. Calculate the mean and standard deviation of the sample. So, the estimated population mean will be same as the sample mean.

You can also calculate the confidence interval of the sample mean using the formula -

CI = (sample mean - Z (s/n), sample mean + Z (s/n))

Where s is the sample standard deviation and n is the sample size ( greater than 30).

And Z is the standard normal distribution value for the reqyirwd level of significance.

If we use a smaller sample size, then instead of Z we will use the t-distribution with degree of freedom = n-1 and required level of significance.