Download Test Name: Exam #4c Practice 1. A racing car consumes a mean of

Test Name: Exam #4c Practice
1.
A racing car consumes a mean of 96 gallons of gas per race with a standard deviation of 5. If 36 racing cars are randomly
selected, what is the probability that the sample mean would be less than 97.2 gallons? (Round your answer to 4 decimal
places)
2.
A quality control expert at LIFE batteries wants to test their new batteries. The design engineer claims they have a variance
of 5476 minutes with a mean life of 980 minutes. If the claim is true, in a sample of 98 batteries, what is the probability that
the mean battery life would differ from the population mean by greater than 11.6 minutes? (Round your answer to 4 decimal
places)
3.
The mean output of a certain type of amplifier is 336 watts with a standard deviation of 12. If 59 amplifiers are sampled,
what is the probability that the mean of the sample would differ from the population mean by less than 0.7 watts? (Round
your answer to 4 decimal places)
4.
Given the following confidence interval for a population mean, compute the margin of error, .
5.
A random sample of 4 fields of spring wheat has a mean yield of 33.2 bushels per acre and standard deviation of 7.44 bushels
per acre. Determine the 99% confidence interval for the true mean yield. Assume the population is approximately normal.
Step 1. Find the critical value that should be used in constructing the confidence interval. (Round answer to 3 decimal places)
Step 2. Construct the 99% confidence interval. (Round answer to 1 decimal place)
Lower Bound:
Upper Bound:
6.
A physicist examines 24 sedimentary samples for magnesium concentration. The mean magnesium concentration for the
sample data is 0.094 cc/cubic meter with a standard deviation of 0.0596. Determine the 80% confidence interval for the
population mean magnesium concentration. Assume the population is approximately normal.
Step 1. Find the critical value that should be used in constructing the confidence interval. (Round answer to 3 decimal places)
Step 2. Construct the 80% confidence interval. (Round answer to 3 decimal places)
Lower Bound:
Upper Bound:
7.
8.
A research scholar wants to know how many times per hour a certain strand of virus reproduces. He obtains information
from 20 strands of this particular virus and finds the mean to be 9. The population distribution is assumed to be uniformly
distributed. Determine which of the following methods would be most appropriate when calculating the margin of error for
the population mean:
A) Normal B) Student C) More
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A toy manufacturer wants to statistic
know how many new toys children buy each year. Suppose a sample of size 725 is drawn from
the population with ̅
6.9.alAssume
1.8 Construct the 90% confidence interval for the mean number of toys. (Round
techniqu
your answers to 1 decimal place)
es
Lower Bound:
Upper Bound:
9.
Suppose a research company desires to know the mean consumption of beef per week among people over 33. They believe
that beef consumption has a mean of 3.5 lbs. Assume the standard deviation is known to be 1.2. How large a sample would
be required in order to estimate mean weekly consumption of beef by people over 33 at the 85 % confidence level with an
error of at most 0.06 lbs.? (Round your answer up to the next integer)
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