Question

n a rural area, only about 30% of the wells that are drilled find adequate water at a depth of 100 feet or less. A local man claims to be able to find water by "dowsing"—using a forked stick to indicate where the well should be drilled. You check with 80 of his cus- tomers and find that 27 have wells less than 100 feet deep. What do you conclude about his claim?

Answer 1

Answer: the man's claim is true.

Explanation:

Given that 30% of the well find water at a depth <=100 feet

P(X<=100) = 0.30

If the man's prediction work well the probability of finding well at less than 100 or equal should be high fwhen calculated from his results. So give 27 out of 80 wells

P(X<=100) = 27/80

P(X<=100) = 0.3375

Since 0.3375 > 0.3

The man's claim is true.