Exercise 10 Page 627

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a In a survey, we asked 271 students in our class whether they attending the class field trip. One hundred twenty-one males respond, 92 of which are attending the trip. Thirty-one females are not attending the field trip. We will find and interpret the marginal frequencies. To do so, let's put these values in a two-way table.

We need to find the missing values in the table. Recall that the sum of the marginal frequencies in the total row and the total column should each equal the total observations. With this information we can find the number of females surveyed by subtracting 121 from 271.

271-121= 150 Females Additionally, a marginal frequency is given by the sum of the joint frequencies. In a similar way, we can find the number of males who are not attending the field trip by subtracting 92 from 121. 121-92= 29 Males Let's write these values in our table.

Now, we can find the number of students who are not attending the trip by adding the joint frequencies, 29+31= 60. Additionally, by subtracting 31 from 150 we could find the missing joint frequency, 150-31= 119. Finally, the number of students who are attending the trip is given by 92+ 119= 211. Let's complete our table.

From the table, we can see that a total of 271 students were surveyed, 211 of which are attending the trip. Additionally, 121 males were surveyed and 120 females were surveyed.

b Note that the column total shows the total number of females and males. Therefore, we need to find the conditional relative frequencies using column totals to find the percent of females who are attending the class field trip.

Therefore, about 79 % of females are attending the class field trip.

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Exercise 10 Page 627

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