Question

QUESTION 1:

Researchers gave 20 index cards to a waitress at an Italian restaurant in New Jersey. Before delivering the bill to each customer, the waitress randomly selected a card and wrote on the bill the same message that was printed on the index card. 20 of the cards had the message "The weather is supposed to be really good tomorrow. I hope you enjoy the day!" Another 20 cards contained the message "The weather is supposed to be not so good tomorrow. I hope you enjoy the day anyway!" After the customers left, the waitress recorded the amount of the tip (percent of bill) before taxes. Here are the tips for those receiving the good-weather message:

20.7	18.8	19.8	20.9	22	23.6	22.8	25.1	22.2	20
24.8	22.2	26.9	20.6	21.9	23.9	21	22.2	21.8	22.7

The tips for the 20 customers who received the bad-weather message are

18	19	19.5	18.5	18.3	19.2	18.7	16.2	16.7	14.2
16.9	13.3	17.5	19.8	20.4	18.7	18.2	23.2	18.1	19.2

What degrees of freedom would you use in the conservative two-sample t procedures to compare the percentage of tips when the forecast is good and bad?

What is the two-sample t test statistic?

Test the hypothesis of the two different messages produce different percent tips for αα = 10%

The null hypothesis of no difference in tips due to the weather "forecast" is

rejected

not rejected

QUESTION 2:

A study of commuting times reports the travel times to work of a random sample of 22 employed adults in Chicago. The mean is x¯¯¯x¯ = 33.33 minutes and the standard deviation is s = 25.89 minutes.

What is the standard error (±0.0001) of the mean?  

Answer 1