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15 test subjects are asked if they prefer brand A, brand B, or have no preference. 9 prefer brand A, 3 prefer brand B and 3 have no preference. What is the P-value for a sign test of no difference between brands?
Thanks in advance for any help guys, I'm really stuck
Hey jamie9.
Can you show us what you have tried?
Yes sorry if this doesn't make sense...
Okay so I was thinking for no difference H0: µ = 7.5 and H1: µ ≠ 7.5.
Then I wanted to use a z test and test for ≥ 7.5 where B(15, 0.5) but the standard deviation wasn't given so I assumed I was on the wrong track?
When you say sign test, I thought you wanted to do a non-parametric test for this data.
Given this data you have three choices and it might make sense if you allocated brand A to -1, no preference to 0, and brand B to +1 and then used a test that checked whether the median of this sample was statistically equal to 0 (given some confidence level) or whether you could reject this claim (or hypothesis) with the data.