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bachelor in business administration
Polytechnic State University Sanluis
Jan-2006 - Nov-2010
CPA
Polytechnic State University
Jan-2012 - Nov-2016
Professor
Harvard Square Academy (HS2)
Mar-2012 - Present
Refer to Exercise 7.60. Suppose that n1 = n2 = n, and find the value of n that allows the difference between the sample means to be within .04 unit of μ1 − μ2 with probability .90.
Exercise 7.60
The result in Exercise 7.58 holds even if the sample sizes differ. That is, if X1, X2, . . . , Xn1 and Y1, Y2, . . . , Yn2 constitute independent random samples from populations with means μ1 and μ2 and variancesÂ
  andÂ
, respectively, then X − Y will be approximately normally distributed, for large n1 and n2, with mean μ1 − μ2 and varianceÂ
 The flow of water through soil depends on, among other things, the porosity (volume
proportion of voids) of the soil. To compare two types of sandy soil, n1 = 50 measurements are to be taken on the porosity of soil A and n2 = 100 measurements are to be taken on soil B.
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Exercise 7.58
Suppose that X1, X2, . . . , Xn and Y1, Y2, . . . , Yn are independent random samples from populations with means μ1 and μ2 and variancesÂ
 andÂ
 respectively. Show that the random variable
![]()
satisfies the conditions of Theorem 7.4 and thus that the distribution function of Un converges to a standard normal distribution function as n → ∞.
Theorem 7.4

Â
Â
Â
Â
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