Recall Example 7.3 about adding a laugh track to dad jokes to make them funnier. The researchers investigated two kinds of laugh tracks—one with posed laughter and one with spontaneous laughter. Recall that to create the posed laughter laugh track, the researchers asked people to laugh and recorded the results. The researchers also tested the same 40 jokes with a spontaneous laughing laugh track, which they created by having people watch funny videos and recording their laughter. The data can be found in the file LaughTypes. Put these data into the Matched Pairs applet to investigate whether the type of laughter makes a difference in the ratings of the jokes. 

a. State the relevant hypotheses in words. 

b. What is the mean rating of the jokes for each condition? What is the mean of the differences in ratings? 

c. Determine and report the t-statistic and theory-based p-value. 

d. Based on the t-statistic and p-value, is there strong evidence that the type of laughter makes a difference in how funny people think the jokes are? Explain.