The quality control department of a paper company measures the brightness (a measure of reflectance) of finished paper on a periodic basis throughout the day. Two instruments that are available to measure the paper specimens are subject to error, but they can be adjusted so that the mean readings for a control paper specimen are the same for both instruments. Suppose you are concerned about the precision of the two instruments and want to compare the variability in the readings of instrument 1 with those of instrument 2. Five brightness measurements were made on a single paper specimen, using each of the two instruments. The data are shown in the following table.
Instrument1.................................Instrument2
29.................................... 26
28.................................... 34
30.................................... 30
28.................................... 32
30.................................... 28
a. Is the variance of the measurements obtained by instrument 1 significantly different from the variance of the measurements obtained by instrument 2?
b. What assumptions must be satisfied for the test in part a to be valid?