G. Estimates and Sample Sizes

Two major activities of inferential statistics are (1) estimate values of population parameters and (2) test claims made about population parameters. This chapter is the first major introduction to inferential statistics. You will be setting up confidence intervals to estimate the true value of a population parameter. A very important facet of research is the determiniation of sample size. You will find that the size of the sample depends on the desired confidence level, the desired margin of error, and the known estimate of the population parameter. In formulas, we denote the size of the sample as, "n."

You will be using Table A-2 on most of these problems. This table is found in your textbook and it is also located on a detachable Formula/Table card included with the book. You will also need to keep a list of commonly used critical values, found on page 332 in Figure 7-3. This table only has critical values for 90%, 95% and 99% confidence levels, but you can add to it as you solve for the critical values for other confidence levels.

When you get to section 7.4, you will learn about Student t distribution, which is used when the standard deviation of the population is unknown. In these problems, we only have the standard deviation of the sample, called s. Sometimes, you may be given a set of data that you need to enter in your calculator to find the standard deviation of the sample (denoted as Sx in the calculator). To find the critical values associated with Student t distributions, you will be using Table A-3, which is also found in the detachable Formula/Table card.