Two different box-filling machines are used to fill cereal boxes on an assembly line. The critical measurement influenced by the
se machines is the weight of the product in the boxes. Engineers are quite certain that the variance of the weight of product is 1 ounce. Experiments are conducted using both machines with sample sizes of 36 each. The sample averages for machines A and B are 4.5 ounces and 4.7 ounces respectively. Engineers are surprised that the two sample averages for the filling machines are so different. a. Use the CLT to determine the distribution of �$! − �$ ". b. What is �(�$! − �$ " ≥ 0.2)?
1 answer:
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Answer:
a)
And we can find this probability using the normal standard table or excel and we got:
b)
And we can find this probability using the complement rule and the normal standard table or excel and we got:
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Part a
Let X the random variable that represent the time for the step 1 and Y the time for the step 2, we define the random variable R= X+Y for the total time and the distribution for R assuming independence between X and Y is:
Where and
We are interested on this probability
And the best way to solve this problem is using the normal standard distribution and the z score given by:
If we apply this formula to our probability we got this:
And we can find this probability using the normal standard table or excel and we got:
Part b
And we can find this probability using the complement rule and the normal standard table or excel and we got: