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Leticia wants to estimate what proportion of her school's seniors plan to attend the prom. She interviews a simple random sample (SRS) of 50 of the 750 seniors in her school and finds that 36 plan to go to the prom. Construct and interpret a [tex]$90\%$[/tex] confidence interval for the proportion of all seniors at Leticia's school who plan to go to the prom.

State: [tex]\square[/tex]

Plan: [tex]\square[/tex] One-sample [tex]z[/tex] interval for [tex]p[/tex].

Random? [tex]\square[/tex]

Large Counts? [tex]n \hat{p} = \square[/tex] and [tex]n(1-\hat{p}) = \square[/tex]

The conditions for inference [tex]\square[/tex] met.

Answer :

To solve the problem, we need to construct a confidence interval for the proportion of seniors at Leticia's school who plan to attend the prom. Here's a step-by-step solution:

### State:
Leticia wants to estimate the proportion of seniors at her school who plan to attend the prom. She takes a simple random sample (SRS) of 50 seniors and finds that 36 of them plan to go.

### Plan:
We'll use a one-sample [tex]\( z \)[/tex] interval for proportions to construct the confidence interval.

### Random?
Leticia used a simple random sample (SRS) of 50 seniors, so the condition for randomness is met.

### Large Counts Condition:
To use a normal approximation, we check that both [tex]\( n\hat{p} \)[/tex] and [tex]\( n(1 - \hat{p}) \)[/tex] are at least 10.

- [tex]\( n\hat{p} = 50 \times (36/50) = 36 \)[/tex]
- [tex]\( n(1 - \hat{p}) = 50 \times (1 - 36/50) = 14 \)[/tex]

Since both values are greater than 10, the Large Counts condition is satisfied.

### Calculate the Confidence Interval:

1. Sample Proportion ([tex]\(\hat{p}\)[/tex]):
[tex]\[
\hat{p} = \frac{36}{50} = 0.72
\][/tex]

2. Standard Error (SE):
[tex]\[
\text{SE} = \sqrt{\frac{\hat{p}(1 - \hat{p})}{n}} = \sqrt{\frac{0.72 \times 0.28}{50}}
\][/tex]

3. Margin of Error (ME):
To find the Margin of Error, we multiply the standard error by the [tex]\( z^* \)[/tex] value for a 90% confidence level, which is 1.645.
[tex]\[
\text{ME} = 1.645 \times \text{SE}
\][/tex]

4. Confidence Interval:
The confidence interval is given by:
[tex]\[
\hat{p} \pm \text{ME}
\][/tex]

Plugging in our numbers:
- Lower bound: [tex]\( 0.6155 \)[/tex]
- Upper bound: [tex]\( 0.8245 \)[/tex]

### Conclusion:
With 90% confidence, we estimate that the proportion of all seniors who plan to attend the prom at Leticia's school is between approximately 61.55% and 82.45%. The conditions for inference were met, so this estimate should be reliable.

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