Answer:
A. 5
Step-by-step explanation:
It says that the sample is normally distributed, which means it follows the bell curve in terms of spreading. That means that 68% of the numbers are within two standard deviations, centered on the mean, one standard deviation below, one up.
That's confirmed by the fact that 1,360 numbers (exactly 68% of 2,000) are between 40 and 50. Since the mean is 45, that gives a spread of ± 1 standard deviation for 68% of the numbers.
One standard deviation goes from 40 to 45, another from 45 to 50.
So, the standard deviation of this sample is 5.
