1. An automotive repair shop has determined that
* the average service time*
on an automobile

is *2
*** hours**
with

is selected.

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(a) What is the probability that the sample of 64 will have a mean service time

** greater
than 114 minutes**?

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(b) Assume the population
consists of ** 400 services**.
Determine

**the
standard error of the mean.***(to
2 digits)*

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2. In a large university,**
20% **of the students are business
majors. A random sample of

** 100
students** is selected,
and their majors are recorded.

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(a) Compute *the
standard erro** r*
of the proportion.

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** at
least 12** business majors?

**(to
4 digits)**

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** (**c)
What is the probability that the sample contains

**(to 3 digits)**

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(d) What is the probability that the sample contains
** less than 15** business
majors?

**(to 4 digits)**

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3. ** The average**
daily earnings of bus drivers in a city is

Assume that we select a random sample of ** 81**
bus drivers from a population of

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(a) What is ** the standard error of the
mean**?

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(b) What is the probability that
the sample mean will be *greater than $960*?
*(to 4 digits)*

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4. There are ** 500
employees** in a firm,

selected randomly.

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(a) Determine ** the
standard error of the proportion**.

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(b) What is the probability that the sample proportion
of females is ** between 0.4 and 0.55**?

**(to 4 digits)**

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