STAT 211 Module 9 HW Quiz Final
When testing a new treatment, what is the difference between statistical significance and practical
significance? Can a treatment have statistical significance, but not practical significance? Statistical
significance is achieved when the result is very unlikely to occur by chance. Practical significance is
related to whether common sense suggests that the treatment makes enough of a difference to justify
its use. It is possible for a treatment to have statistical significance, but not practical significance.
What is the goal of statistics? To learn to distinguish between statistical conclusions that are likely to be
valid and those that are seriously flawed.
Determine whether the underlined number is a statistic or a parameter. A sample of employees is
selected and it is found that 40% own a vehicle. Statistic because the value is a numerical measurement
describing a characteristic of a sample.
Determine which of the four levels of measurement (nominal, ordinal, interval, ratio) is most appropriate
for the data below. Diameter of circles in inches. The ratio level of measurement is most appropriate
because the data can be ordered, differences (obtained by subtraction) can be found and are
meaningful and there is a natural starting zero point.
Identify the type of sampling used (random, systematic, convenience, stratified, or cluster sampling) in
the situation described below. In a poll conducted by a certain research center, 1081 adults were called
after their telephone numbers were randomly generated by a computer, and 38% were able to correctly
identify the secretary of state. Random sampling
Among fatal plane crashes that occurred during the past 70 years, 408 were due to pilot error, 60 were
due to other human error, 605 were due to weather, 106 were due to mechanical problems, and 119
were due to sabotage. Construct the relative frequency distribution. What is the most serious threat to
aviation safety, and can anything be done about it? Pilot error 31.4%, Other human error 4.6%, Weather
46.6%, Mechanical problems 8.2%, Sabotage 9.2%. Weather is the most serious threat to aviation
safety. Weather monitoring systems could be improved.
Natural births randomly selected from four hospitals in a highly populated region occurred on the days
of the week (in the order of Monday through Sunday) with the frequencies 53, 63, 72, 59, 57, 43, 53.
Does it appear that such births occur on the days of the week with equal frequency? Monday 13.25%,
Tuesday 15.75%, Wednesday 18%, Thursday 14.75%, Friday 14.25%, Saturday 10.75%, Sunday 13.25%.
Yes, it appears that births occur on the days of the week with frequencies that are about the same.
Outliers are sample values that lie very far away from the majority of the other sample values.
In a relative frequency distribution, the frequency of a class is replaced with a proportion or percent.
Heights of adult males are normally distributed. If a large sample of heights of adult males is randomly
selected and the heights are illustrated in a histogram, what is the shape of that histogram? Bell-shaped
A sample of blood pressure measurements is taken from a data set and those values (mm Hg) are listed
below. The values are matched so that subjects each have systolic and diastolic measurements. Find the
mean and median for each of the two samples and then compare the two sets of results. Are the
measures of center the best statistics to use with these data? What else might be better?
Systolic 110 148 100 104 97 128 109 108 158 135
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