To find the point estimate of the proportion of all light bulbs that last more than 500 hours, you can use the formula for the sample proportion \( \hat{p} \):
\[ \hat{p} = \frac{x}{n} \]
where:
- \( x \) is the number of successes (the number of light bulbs that lasted more than 500 hours), and
- \( n \) is the total number of trials (the total number of light bulbs tested).
In this case:
- \( x = 224 \)
- \( n = 430 \)
Now, substitute the values into the formula:
\[ \hat{p} = \frac{224}{430} \approx 0.5209302 \]
Now, rounding this to the nearest thousandth gives:
\[ \hat{p} \approx 0.521 \]
So the point estimate of the proportion of all light bulbs that last more than 500 hours is:
A) 0.521
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