People tend to be more generous after receiving good news. Are they less generou

Question

People tend to be more generous after receiving good news. Are they less generous after receiving bad news? The average tip left by adult Americans is 22%. Give 20 patrons of a restaurant a message on their bill warning them that tomorrow's weather will be bad and record the percentage tip they leave. Here are the tips as a percentage of the total bill:

18 19.1 19.2 18.8 18.4 19 18.5 16.1 16.8 18.2

14 17 13.6 17.5 20 20.2 18.8 18 23.2 19.4

Suppose that percentage tips are Normal with =2.3.

The P-value (±±0.001) is

Explanation / Answer

Mean = 22

Standard deviation = 2.3

Mean of the sample = sum( tips) /20 = 363.9/20 = 18.195

P(|X|<(22-18.195)/2.3) = 0.9019

Hence the p value is 1-0.9019 = 0.0981

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