Answer:
The approximate percentage of lightbulb replacement requests numbering between 47 and 68 is 49.85%.
Step-by-step explanation:
The Empirical Rule states that, for a normally distributed random variable:
Approximately 68% of the measures are within 1 standard deviation of the mean.
Approximately 95% of the measures are within 2 standard deviations of the mean.
Approximately 99.7% of the measures are within 3 standard deviations of the mean.
In this problem, we have that:
Mean of 47
Standard deviation of 7
What is the approximate percentage of lightbulb replacement requests numbering between 47 and 68?
The normal distribution is symmetric, which means that 50% of the measures are below the mean and 50% of the above.
Between 47 and 68:
68 = 47 + 7*3
So 68 is three standard deviations of the mean.
Of the 50% above the mean, approximately 99.7% are between the mean of 47 and 3 standard deviations above the mean, which is 68. So
0.5*0.997 = 0.4985
0.4985*100 = 49.85%
The approximate percentage of lightbulb replacement requests numbering between 47 and 68 is 49.85%.
