Statistics with Probability

You must be logged in to reply to this topic.

  • Author
    Posts
  • #12945

    Afzal
    Participant

    i did this problem but i think i did some thing wrong. can you point out the mistake and how to draw it?

    no-1 page-311

    μ=128
    σ=16
    a. when n=9 then sd(xi)=16*√9=48, E[x]=9*128=1152
    b when n=25 then sd(xi)=16*√25=80, E[x]=25*128=3200
    c. when n=100 then sd(xi)=16*√100=160 E[x]=100*128=12800
    a.124< X >132
    124-1152132-1152
    -10028/48< (X-1152)/48>-1020/48
    -21.42-21.25
    =normdist(-21.25)-=normdist(-21.42)
    b..124132
    124-3200132-3200
    -3068/80<(X-3200)/80>-3068/80
    -38.45-38.35
    =normdist(-38.35)-=normdist(-38.45)
    c.
    124132
    124-12800132-12800
    -12676/160<(X-128)/160>-12668/160
    -79.23-79.18
    =normdist(-79.18)-=normdist(-79.23)

    #16194

    Ezra Halleck
    Participant

    Main problem is that you are using the wrong formula. For the std dev of the sample mean, you need to divide by the sqrt(n) and not multiply.

Viewing 2 posts - 1 through 2 (of 2 total)

You must be logged in to reply to this topic.