Problem 9-8 (modified). The height of adult males in a particular city is normally distributed, with mean 69.5 in. and standard deviation 2.65 in. When a random sample is taken of size 20, find (1) the standard error of Xbar

Complete Question

Problem 9-8 (modified). The height of adult males in a particular city is normally distributed, with mean 69.5 in. and standard deviation 2.65 in.

When a random sample is taken of size  20, find (1) the standard error of Xbar

(2) the probability that Xbar falls within .5 in. of the true mean

Probability=

1

2

Step-by-step explanation:

From the question we are told that

  The true  mean is  

  The standard deviation is  

    The sample size is n =  20

Generally the standard error of Xbar is mathematically represented as

=>  

=>  

Generally for   to fall within 0.5 of the true mean the must be within

=>  

=>  

or  

=>    

=>    

Generally the probability that   fall with 0.5  of the true mean is mathematically represented as

=>  

=>  

From the z table the probability of  (  Z    < 0.844)  and   (  Z    < -0.844)  is  

and

So

=>  

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step-by-step explanation:

answer: first option i.e. 'a' is correct.

step-by-step explanation:

since we have given that

number of minutes to wrap a small gift box = 4 minutes

we need to find the number of gifts to be wrapped in 5 minutes

since there is a direct variation, as the number of minutes will increase with   number of gifts to be wrapped.

so, let the number of gifts to be wrapped in 5 minutes be x.

so, it becomes,

hence, first option 'a'   is correct.