If 9% of the thermometers are rejected because they have readings that are too high, but all other thermometers are acceptable, find the temperature that separates the rejected thermometers from the others.

To find the answer to this question, plot the frequency distribution of the temperatures measured by the thermometers. To do this, order the temperature readings from highest to lowest. Assign  a rank number 1 to the highest reading, 2 to the second highest and so on. Now for each reading, calculate the frequency distribution value that will be plotted on the X-axis: P = rank/(n + 1) * 100
were n is the total number of readings.

Now plot the temperature readings on the Y-axis and the P values, which will be a percentage, on the X-axis. The temperature you are looking for will be the Y-axis value corresponding with the value 9% on the X-axis

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