Every 90 minutes routine readings are made of the level of a

Every 90 minutes routine readings are made of the level of asbestos fiber
present in the air of an industrial plant. A salesperson claimed that spraying
with chemical S-142 could be beneficial. Arrangements were made for
a comparative trial in the plant itself. Four consecutive readings, the first
without S-142 and the second with S-142 were as follows: 8, 6, 3, and 4. In
light of past data collected without S-142, given below, do you think S-142
works? Explain your answer.

Asbestos Data, 112 Consecutive Readings
November 2| 9 10 9 8 9 8 8 8 7 6 9 10 11 9 10 11
November 3| 11 11 11 10 11 12 13 12 13 12 14 15 14 12 13 13
November 4| 12 13 13 13 13 13 10 8 9 8 6 7 7 6 5 6
November 5| 5 6 4 5 4 4 2 4 5 4 5 6 5 5 6 5
November 6| 6 7 8 8 8 7 9 10 9 10 9 8 9 8 7 7
November 7| 8 7 7 7 8 8 8 8 7 6 5 6 5 6 7 6
November 8| 6 5 6 6 5 4 3 4 5 5 6 5 6 7 6 5

Not sure where to start.

Solution