# simple random sample

1. ### (Solved) Drawback of random sampling - need someone to explain better

This is what my research skills book mentions: The first few hundred cases selected using simple random sampling normally consist of bunches of cases whose numbers are closer together followed by a gap and then further bunching. For more than a few hundred cases, this pattern occurs far less...
2. ### Help with proof that expected value of x_i is the populaton mean X bar

I'm having a little trouble with the proof that the expected value of x_i is \bar{X} . What I have is E[x_i]=\sum_{j=1}^{N}X_j Pr(x_i=X_j) Then Pr(x_i=X_j) = 1/N This is the bit I can't understand, how does that probability evaluate to that value. I know the...
3. ### Sampling distribution

Hi, I have to calculate mean and standard deviation of sample means of size 30 (with replacement) from a population of size 87. Its impossible to do it without the help of any software because N^n is 87^30. I tried to get this distribution by using SPSS but it only generates random...
4. ### Simple Random Sample vs Random Sample

Problem: "A computer company employs 100 software engineers and 100 hardware engineers. The personnel manager randomly selects 20 of the software engineers and 20 of the hardware engineers and questions them about career opportunities within the company. Does this sampling plan result in a...