SOLUTION: I made 20 measurements of friction on one type of material with average result of friction 30,5 % and another 20 measurement of friction on second type of material with average res

Question 686885: I made 20 measurements of friction on one type of material with average result of friction 30,5 % and another 20 measurement of friction on second type of material with average result of 35,5 %. Now I would like to know, whether this difference is significant, using alpha 0,05. Please, could you help?
Many thanks.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
I made 20 measurements of friction on one type of material with average result of friction 30,5 % and another 20 measurement of friction on second type of material with average result of 35,5 %. Now I would like to know, whether this difference is significant, using alpha 0,05. Please, could you help?
------
Ho: p1-p2 = 0
Ha: p1-p2 # 0
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test statistic:
z = (0.305-0.355)/sqrt[(0.305*0.695/20) + (0.355*0.645/20)]
= -0.05/0.1485
= -0.3367
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Critical values for 2-tail test with alpha = 5%: +-1.96
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Conclusion: Since the test stat is not in the reject interval,
fail to reject Ho.
There is no significant difference at the 5% level.
Cheers,
Stan H.
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