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1. What Is
"Statistics is a way to get information from data."
Statis- tics?
Statistics is a tool for creating new understanding from a set of
numbers. You need data and information
2. descriptive statis- one of two branches of statistics which focuses on methods of
organizing, sum-
tics marizing, and presenting data in a convenient and informative way.
One form of descriptive statistics uses graphical techniques which allow statistics
practitioners to present data in ways that make it easy for the reader to
extract useful information.
Another form of descriptive statistics uses numerical techniques to
summarize data. Rather than providing the raw data, the professor may
only share summary data with the student.
3. Histogram (or bar graph) can show if the data is evenly distributed across the range of
values, if it falls symmetrically from a center peak (normal distribution), if
there is a peak but the more of the data falls on one side of the peak
than the other (a skewed distribution), or if there are two or more
peaks in the data (bi- or multi-modal).
4. average mean
5. range calculated by subtracting the smallest number from the largest.
6. mode the most frequently occurring score(s) in a distribution
7. variance the average squared deviation from the mean
8. Standard the square root of the variance and gets the variability measure back to the
devia- tion same units as the data. Standard deviation has many useful
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properties when the data is normally distributed
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9. inferential a body of methods used to draw conclusions or inferences about
statis- tics characteristics of populations based on sample data.
Exit polls are a very common application of statistical inference.
10. Statistical population, the sample, and the statistical inference.
infer- ence
problems
involve three
key concepts:
11. Population: the group of all items of interest to a statistics practitioner. It is frequen
very
large and may, in fact, be infinitely large. In the language of statistics,
population does not necessarily refer to a group of people. It may, for
example, refer to the population of diameters of ball bearings
produced at a large plant.
A descriptive measure of a population is called a parameter. In most
applications of inferential statistics, the parameter represents the
information we need.
12. Sample a set of data drawn from the population. A descriptive measure of a sam
is
called a statistic. We use statistics to make inferences about parameters.
13. statistical the process of making an estimate, prediction, or decision about a
infer- ence population based on sample data. Because populations are almost
always very large, in- vestigating each member of the population would
be impractical and expensive.
It is far easier and cheaper to take a sample from the population of
interest and draw conclusions or make estimates about the
population on the basis of information provided by the sample.
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However, such
conclusions and
estimates are not
always going to be
correct. For this reason,
we build into the
statistical inference a
measure of reliability.
There are two such
measures, the
confidence level and
the significance level.
The confidence level
is the proportion of
times that an
estimating procedure
will be correct. When
the purpose of the
statistical inference is
to draw a conclusion
about