- American males 18-74 have heights that are normally
distributed as N(69,3). Wanting to know whether Dutch males
in GR are taller than average, you take a random sample of
55 and get a mean height of 70.2".
Ans: (z = 2.97, P = 0.0015)
- A cola company says it fills its 2-liter bottles, on
average, to 2.01 liters. You purchase 25 bottles, measure
the volume of pop, and find a mean of 1.97 liters and standard
deviation 0.107. Is there strong evidence here that the
company is wrong?
Ans: (t = -1.869, df = 24, 0.05 < P < 0.1)
- A certain company says it helps people perform better on
the SAT-math test. To test their claim, they select 51 people,
give them the test before and after training them, and determine
that the difference in after vs. before performance among these
people is, on average, 19 points with a s.d. of 8 pts. Does the
evidence support their claim?
Ans: (t = 16.96, df = 50, P < 0.0005)
- A survey of 115 residents of a certain mid-sized city
reveals a proportion of 57% who identify themselves as
Republican. Is the evidence significant at the 5% level that
this is a "Republican town"?
Ans: (z = 1.50, P = 0.0668)