By the definition, An observed value of \bar{x} to estimate the mean of population is a point estimate and the statistic \bar{x} is a poiont estimator.
It is given that, "Hen 430 randomly selected light bulbs were tested in a laboratory"
That is, the Random sample size n= 430
The statement given that, "224 lasted more than 500 hours"
So x=224
Now find a point estimate of the last more than 500 hours proportion of all light bulbs:
Thus [tex] p=\frac{x}{n}=\frac{224}{430} [/tex]
This implies that [tex] p=0.5209\sim0.521 [/tex]
Thus the answer is D: 0.521.
