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April 1st, 2007, 05:42 AM   #1
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Null Hypothesis and Test of Significance

Weekly sales of regular ground coffee at a supermarket have in the recent
past varied according to a normal distribution with mean mu=354 units per
week and std. dev. sigma =33 units. The store reduces the prce by 5%. Sales
in the next three weeks are 405,378 and 411 units. Is this good evidence
that average sales are now higher?
Ho: mu = 354
Ha: mu > 354

a.)Find the value of the test statistic xbar

b.)Sketch the normal curve for the sampling distribution of xbar when null
hypothesis(Ho) is true. Shade the area that represents the P-value for the
observed outcome.

c.)Calculate the P-value

d.)Is the result statistically significant at the alpha = .05 level? Is it
significant at the alpha = .01? Do u think there is convincing evidence
that mean sales are higher?
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