Solution: We are given:


Now let's find the estimated value of standard deviation using the range rule of thumb. According to range rule of thumb, the estimate of standard deviation is:

Therefore the estimated standard deviation is 0.690
is this an acceptable approximation?
Answer: c. Yes, because the error of the range rule of thumb's approximation is less than 15%.
Explanation:
The difference between estimated standard deviation and actual standard deviation is:
0.807 - 0.690 = 0.117
Now let's find the percentage of error
.
Therefore, the error of the range rule of thumb's approximation is less than 15%.