Proctor & Gamble claims that at least half the bars of Ivory soap they produce are 99.44% pure (or more pure) as advertised. Unilever, one of Proctor & Gamble's competitors, wishes to put this claim to the test. They sample the purity of 149 bars of Ivory soap. They find that 68 of them meet the 99.44% purity advertised.
Calculate the p-value.
Claim :At least half the bars of Ivory soap they produce are 99.44% pure (or more pure) as advertised.
Here we have to test that
where
n = number of bars of Ivory soap selected randomly = 149
x = number of bars of Ivory soap meet the 99.44% purity advertised = 68
Sample proportion:
(Round to 4 decimal)
Test statistic:
z = -1.06 (Round to 2 decimal)
Test statistic = z = -1.06
P value:
Test is right tailed test.
P value= P(z > -1.06)
= 1 - P(z < -1.06)
= 1 - 0.1446 (From statistical table of negative z values)
= 0.8554
P value = 0.8554
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