[R] One-sample test for p

rr400 raul.felipe.ramirez at gmail.com
Thu Oct 16 12:08:02 CEST 2008


Hi, i am doing a statistics course and am having trouble with an exercise
where i need to determine whether my success rate at something is higher
than 80%. 
I was successful in 29 out of 60 trials, so these were the commands i
entered into R:
>n=60
>p.hat=29/n
>p.0=0.8
>se.0=sqrt(p.0*(1-p.0)/n)
>z=(p.hat-p.0)/se.0
>print(z)
Which returned:
[1] -6.132224
>1-pnorm(z)
Which returned
[1] 1

My problem is that i am meant to state a null and alternative hypothesis
which at the moment i have stated as  p>0.8 (null) and p≤0.8 (alternative).
As things stand, though, a p-value of 1 suggests i should reject the null
hypothesis which can't be right since i am obviously successful less than
80% of the time. 
I am not sure where i am getting muddled. Any advice would be greatly
appreciated. Thanks!
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