Suppose your company produces potato chips. The most popular size is the 14 ounce package. You want to find out if the net weights of the 14 oz. packages of chips being produced are actually 14 oz.

Here are some key issues concerning the packaging process.

	Bags should contain the advertised net weight. Rarely should a package contain less than 14 oz.
	In meeting or exceeding the advertised net weight, the amount of overfill needs to be small.
	The filling process needs to be as consistent, with small variability.

The net weights of all 14 oz. packages coming off the production line form the population of the study. Note that even though the subject of the data collection is called the population, it does not actually have to be people.

To study the fill weights, you could weigh an individual package, some of the packages, or all of the packages.

It may not be practical to weigh every bag made (the whole population). We may be opening the bags, to weigh just the contents– destructive testing.

One package may not be representative of the whole production, because in choosing one package you could get one that had an unusually high or low number of chips.

Several packages (a sample) taken from the production line or from store shelves will better represent the population than just one package. A sample is a smaller group taken from the population under study.

#1 State one plan you could use to obtain a sample.

Suppose you decide to take a sample of ten packages from the production line. The net weights of the ten packages of chips are 14, 16, 14, 14, 15, 13, 15, 17, 13, 14. This sample will represent the larger population of all packages produced. An individual is the name given to one observation or one data point, in this case, the net weight of one package of chips. There are ten individuals in this sample.

An example of data analysis

Making a chart of the data helps reveal trends or other features of the process. This is one method of analysis. Descriptive statistics describe the sample, without trying to say anything about the population. In the sample above, one descriptive statistic is the average weight, 14.5 ounces.

#2 Describe one way you would chart the results of your weight sampling.

An example of statistical inference

If we use the results of the sample to say something about the population, we would be practicing inferential statistics, because we are making an inference or a generalization from our samples out to a whole population . An example of inferential statistics is the statement , "the average net weight made by this particular production line is between 14.3 and 14. 7 ounces with 95% confidence".