statistics
posted by RAJESH on .
drawer contains 50 bolts and 150 nuts. Half of the bolts and half of the nuts are rusted. If one item is chosen at random, what is the probability that it is rusted or a bolt ? In a study to test whether there is a difference between the average height of adult females born in two different
countries, random samples yielded the following results :
n1 = 12O, X1 = 62.7 , S1 = 2.50
n2: 150, X2 : 61.8 , S2 = 2.62
where the measurements are in inches. Use 0.05 level of significance to test the difference between tire average heights.

First question: onehalf = 50%
"X" is typically used to stand for a raw score. If you don't have the symbol, you can write out "mean."
Z = (μ1  μ2)/Standard error of difference between means (SEμμ)
SEμμ = √(SEμ1^2 + SEμ2^2)
SEμ = SD/√(n1)
You are looking for z > 1.96 to reject Ho at .05 level.
I'll let you do the calculations.