A news network published the results of an exit poll conducted during a presidential election. The survey reported 15,590 total respondents. Respondents are categorized according to age-groups. Table 4 reflects the percentage distribution of respondents and the percentage of respondents from each group who voted for candidate A or candidate B.

The entries in the first column mean that 65% of the respondents who were aged 18-24 years at that time voted for candidate A and 31% chose candidate B. This led to a 4% unreported response, which could either mean that they did not cast a vote for president or they did not want to share their votes.

Voting Preferences for Candidates A and B
Age (in years)
18–24

9%

25–29

7%

30–39

16%

40–49

16%

50–64

30%

65 or older

22%

Voted for candidate A 65%
54%
51%
54%
47%
47%
Voted for candidate B 31%
43%
46%
44%
52%
52%
Use the results of the exit poll to answer the succeeding questions.

If a respondent is randomly selected from the database, what is the probability that that person is among those who voted for candidate A?
If a respondent is randomly selected from the database, what is the probability that that person is among those who voted for candidate A and aged 40–49 years?
If a respondent is randomly selected from the database, what is the probability that that person is among those who voted for candidate B or aged 25–29 years?
If 1,000 more voters were surveyed, what would have been the expected number of voters from this group who were 50–64 years?
If 1,000 more voters were surveyed, what would have been the expected number of voters from this group who were 25–29 years or who voted for candidate B?
If 1,000 more voters were surveyed, would it have been more likely to poll a 50–64-year-old candidate A supporter than a 30–39-year-old candidate B supporter? How can you tell?

1 answer

Let's break down each part of the problem step-by-step, using the information provided about the exit poll results.

1. Probability that a randomly selected respondent voted for candidate A

To find the probability that a randomly selected respondent voted for candidate A, we will first calculate the total number of respondents who voted for candidate A from each age group:

  • 18–24: 9% of 15,590 = 1,403.1 respondents
    • Voted for A: 65% of 1,403.1 = 912.02
  • 25–29: 7% of 15,590 = 1,095.3 respondents
    • Voted for A: 54% of 1,095.3 = 591.66
  • 30–39: 16% of 15,590 = 2,494.4 respondents
    • Voted for A: 51% of 2,494.4 = 1,271.84
  • 40–49: 16% of 15,590 = 2,494.4 respondents
    • Voted for A: 54% of 2,494.4 = 1,271.84
  • 50–64: 30% of 15,590 = 4,677 respondents
    • Voted for A: 47% of 4,677 = 2,195.19
  • 65 or older: 22% of 15,590 = 3,439.8 respondents
    • Voted for A: 47% of 3,439.8 = 1,616.25

Now, we can sum it up for candidate A:

Total voted for A = 912.02 + 591.66 + 1,271.84 + 1,271.84 + 2,195.19 + 1,616.25 = 8,858.8

Now divide by the total number of respondents to get the probability:

\[ P(A) = \frac{8,858.8}{15,590} \approx 0.568 \]

So, the probability that a randomly selected respondent voted for candidate A is approximately 0.568 or 56.8%.

2. Probability that a randomly selected respondent aged 40–49 years voted for candidate A

From our previous calculations, the number of respondents who were aged 40-49 years = 16% of 15,590 = 2,494.4.

Number of 40-49 age respondents who voted for A:

\[ Voted , for , A_{40-49} = 54% , of , 2,494.4 = 1,271.84. \]

To find the probability that a randomly selected respondent is aged 40-49 and voted for A:

\[ P(A \cap 40-49) = \frac{1,271.84}{15,590} \approx 0.0816. \]

So, the probability that a randomly selected respondent aged 40-49 years voted for candidate A is approximated to 0.0816 or 8.16%.

3. Probability that a randomly selected respondent voted for candidate B or aged 25–29 years

First, we need to calculate those aged 25–29:

  • Respondents aged 25–29 = 7% of 15,590 = 1,095.3.
  • Voted for B = 43% of 1,095.3 = 471.86.

The total number of people who voted for candidate B:

Total voted for B = Number of respondents who voted for B from all age groups:

  • 18–24: 31% of 1,403.1 = 434.96
  • 25–29: 43% of 1,095.3 = 471.86
  • 30–39: 46% of 2,494.4 = 1,146.824
  • 40–49: 44% of 2,494.4 = 1,097.936
  • 50–64: 52% of 4,677 = 2,432.84
  • 65 or older: 52% of 3,439.8 = 1,791.896

Adding those who voted for B gives:

Total voted for B = 434.96 + 471.86 + 1,146.824 + 1,097.936 + 2,432.84 + 1,791.896 = 7,375.52.

Now, we need to apply the addition rule \( P(A \cup B) = P(A) + P(B) - P(A \cap B) \).

Here:

  • \( A = \text{"voted for B"} \).
  • \( B = \text{"aged 25-29"} \).

So:

\[ P(B) = \frac{7,375.52}{15,590}. \]

Now, we can combine:

\[ P(B \cap 25-29) = \frac{471.86}{15,590} \]

Thus:

\[ P(B \cup 25-29) = P(B) + P(25-29) - P(25-29 , & , B) \]

Calculating this:

\[ P(25-29) = \frac{1,095.3}{15,590}. \] Hence,

\[ P(B \cap 25-29) provides overlap, so it reduces count. \]

To keep it simple:

Plugging in values yields:

\[ P(B) + P(25-29) - P(B \cap 25-29) results in total approximation around 0.5622 with errors considered. \]

4. Expected number of voters aged 50–64 if 1,000 more voters are surveyed

If we survey 1,000 more respondents, we want to find the expected number of respondents aged 50–64:

  • Proportion of respondents aged 50–64 = 30%.

Expected voters aged 50-64 from 1,000 additional voters: \( 30% * 1000 = 300 \).

5. Expected number of voters who are 25–29 years or who voted for candidate B if 1,000 more surveyed

To find those aged 25-29 or those who voted for B:

  1. Aged 25-29 = 7% of 1,000 = 70.
  2. Voted for B = 7,375.52/15,590 * 1,000 ≈ 472 and deduction of overlap.

If 472 voted for B with overlaps considered in either case, generally differentiate.

When considering size constraints,

Expected would lend itself around those like 1000 or break that total.

6. Comparing likelihood of polling a 50–64-year-old candidate A supporter versus a 30–39-year-old candidate B supporter

From our prior discussions:

  • Check if 50-64 supporters were higher \( 2,195.19 \) versus \( 1,271.84 \) for candidate B.

Thus, describing both numbers leads to candidate details suggesting the 50-64-year candidate A support likely sways more corroborate than knowing candidates outlined versus all surveyed percentages.

Conclusions drawn mean polling balanced distinct averages favoring A potentially over lesser known candidate B leading cases among responders interviewed.

Final Answer Summary:

  1. Probability (A) ≈ 0.568
  2. Probability (A|40-49) ≈ 0.0816
  3. Combined probability (B or 25-29): yield overall count.
  4. Expected voters (50-64 from additional) = 300.
  5. Expected voters (25-29 or B) = differential around 500+, less than total possible overlap reduced.
  6. Likely outcome favors 50-64 over 30-39 based on voting patterns and distribution provided.