Question

1.

A) The proportion of residents in Phoenix favoring the building of toll roads to complete the freeway system is believed to be p=0.3. If a random sample of 100 individuals shows that 25 favor building toll roads do we have evidence at the 5% level to claim the true proportion is really lower?

B) A manufacturer produces crankshafts for an automobile engine. The crankshaft's diameter (3cm) is of interest because it is likely to have an impact on warranty claims. A random sample of n=15 shafts is tested and = 2.78cm' It is known that the true deviation in wear is 0.9cm and the wear is normally distributed. Is there evidence that the diameter of the crankshafts is not 3cm?

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Answer 1

A)

  

Hence, we cannot reject H₀ at 5% level of significance.

There is no evidence at the 5% level to claim the true proportion is really lower than 3 cm

B)

We reject H₀ if |Z|>

Hence, we cannot reject H₀ at 5% level of significance.

There is NO evidence that the diameter of the crankshafts is not 3cm