Computing Sample Counts, Percentages and Proportions

A Three Color Bowl Suppose we have a bowl containing marbles, each identical in size, texture and weight, in three colors: Red, Green, Blue.

Draws with Replacement Suppose that we conduct a simple experiment. We shall make a series of draws from the bowl, each with replacement. Color Bowl Mix the Bowl Make a Single Draw from the Bowl Note the Color Drawn and Replace the Marble

Building a Summary – Total Begin by counting the total number of draws made, n. This n is usually called “sample size,” and the symbol “n” is usually the preferred statistical symbol for sample size.

Category Blue Count the number of times that blue shows in our sample. Denote this number as n blue. Compute the sample proportion for blue as p blue = n blue / n. Compute the sample percentage of blue as 100*p blue.

Category Red Count the number of times that red shows in our sample. Denote this number as n red. Compute the sample proportion for red as p red = n red / n. Compute the sample percentage of red as 100*p red.

Category Green Count the number of times that green shows in our sample. Denote this number as n green. Compute the sample proportion for green as p green = n green / n. Compute the sample percentage of green as 100*p green.

Build a Summary Table Colorn color p color pct color Bluen blue p blue = (n blue /n)pct blue = 100*p blue Greenn gree n p green = (n green /n)pct green =100*p green Redn red p red = (n red /n)pct red = 100*p red Totaln1100