Get personalized and accurate responses to your questions with IDNLearn.com. Discover the information you need from our experienced professionals who provide accurate and reliable answers to all your questions.

Fewer young people are driving. In 1995, 63.9% of people under 20 years old who were eligible had a driver's license. Bloomberg reported that percentage had dropped to 41.7% in 2016. Suppose these results are based on a random sample of 1200 people under 20 years old who were eligible to have a driver's license in 1995 and again in 2016.

a. At 95% confidence, what is the margin of error and the interval estimate of the number of eligible people under 20 years old who had a driver's license in 1995?


Sagot :

Explanation:

To find the margin of error and the interval estimate of the number of eligible people under 20 years old who had a driver's license in 1995, we will follow these steps:

1. **Calculate the sample proportion (\( \hat{p} \)) for 1995:**

- Given: \( \hat{p} = 0.639 \)

- Sample size (\( n \)) = 1200

2. **Calculate the standard error (SE):**

\[

SE = \sqrt{\frac{\hat{p} (1 - \hat{p})}{n}}

\]

3. **Find the critical value (\( z \)) for a 95% confidence interval:**

- For a 95% confidence level, \( z \approx 1.96 \)

4. **Calculate the margin of error (ME):**

\[

ME = z \times SE

\]

5. **Calculate the interval estimate:**

\[

\text{Interval estimate} = \hat{p} \pm ME

\]

Let's calculate these step-by-step.

### Step 1: Sample Proportion

\[

\hat{p} = 0.639

\]

### Step 2: Standard Error

\[

SE = \sqrt{\frac{0.639 \times (1 - 0.639)}{1200}}

\]

### Step 3: Critical Value

\[

z = 1.96

\]

### Step 4: Margin of Error

\[

ME = 1.96 \times SE

\]

### Step 5: Interval Estimate

\[

\text{Interval estimate} = \hat{p} \pm ME

\]

Let's do the calculations:

#### Standard Error

\[

SE = \sqrt{\frac{0.639 \times 0.361}{1200}}

\]

\[

SE = \sqrt{\frac{0.230679}{1200}}

\]

\[

SE = \sqrt{0.0001922325}

\]

\[

SE \approx 0.01386

\]

#### Margin of Error

\[

ME = 1.96 \times 0.01386

\]

\[

ME \approx 0.02715

\]

#### Interval Estimate

\[

\text{Lower bound} = \hat{p} - ME = 0.639 - 0.02715 = 0.61185

\]

\[

\text{Upper bound} = \hat{p} + ME = 0.639 + 0.02715 = 0.66615

\]

### Summary

- **Margin of Error (ME):** \( 0.02715 \)

- **Interval Estimate:** \( 0.61185 \) to \( 0.66615 \)

These are the 95% confidence interval estimates for the proportion of eligible people under 20 years old who had a driver's license in 1995.