Answer:
(-16.494 ; -3.506)
Step-by-step explanation:
student Prob A Prob B difference, d (A-B)
1 20 35____ - 15
2 30 40 ___ - 10
3 15 20 ___ - 5
4 40 50 __ - 10
Difference, d = -15, -10, -5, -10
Xd = Σd/ n = - 40 / 4 = - 10
Standard deviation of d ; Sd = 4.082
The confidence interval for the difference is given as :
Xd ± Tcritical*(Sd/√n)
Tcritical at 95%; df = n - 1 ; 4 - 1 = 3
Tcritical(0.05, 3)). = 3.182
C.I = -10 ± 3.182(4.082/√4)
C.I = -10 ± 6.494462
C. I = (-16.494 ; -3.506)
Answer:
3.7
Step-by-step explanation:
We have been given that the distribution of the number of daily requests is bell-shaped and has a mean of 38 and a standard deviation of 6. We are asked to find the approximate percentage of lightbulb replacement requests numbering between 38 and 56.
First of all, we will find z-score corresponding to 38 and 56.


Now we will find z-score corresponding to 56.

We know that according to Empirical rule approximately 68% data lies with-in standard deviation of mean, approximately 95% data lies within 2 standard deviation of mean and approximately 99.7% data lies within 3 standard deviation of mean that is
.
We can see that data point 38 is at mean as it's z-score is 0 and z-score of 56 is 3. This means that 56 is 3 standard deviation above mean.
We know that mean is at center of normal distribution curve. So to find percentage of data points 3 SD above mean, we will divide 99.7% by 2.

Therefore, approximately
of lightbulb replacement requests numbering between 38 and 56.
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