List of Tools for Sampling Distributions
- What students should understand
about this topic:
- What students should be able to DO with this
knowledge:
- Some common misconceptions students
should NOT have:
- Prerequisite knowledge students
should have before using the tools:
- Simulation
Software (Sampling SIM program)
- Pretest:
mostly of prerequisite knowledge, to give before using the tool as a diagnostic
measure.
- Activity
that uses the software.
- Posttest:
including some pretest items, some items directly related to the software,
and some application problems.
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I. What students should understand about this
topic:
- That a sampling distribution for means (based
on quantitative data) is a distribution of sample means
(statistics) of a given sample size, randomly sampled from a
population with mean m and standard deviation s. It is a
probability distribution for the sample mean.
- The sampling distribution for means has the
same mean as the population (parameter)
- As n gets larger, variability of the sample
means gets smaller (a statement, a visual recognition, and
predicting what will happen or how the next picture will
differ)
- Standard error of the mean is a measure of
variability of sample statistic values
- Interpret area/apply areas under curve as
probability statements about sample statistics
- The building block of a sampling distribution
is a sample statistic
- Some values of statistics are more or less
likely than others to be drawn from a particular population
- When it is reasonable to use a normal
approximation
- Different sample sizes lead to different
probabilities for the same value (know how sample size affects the
probability of different outcomes for a statistic)
- Sampling distributions tend to look more
normal than like the population, even for small samples
- As sample sizes get very large, all sampling
distributions for means look alike (i.e., have the same shape),
regardless of the population from which they are drawn
- Averages are more normal and less variable
than individual observations
- Distinguish between a distribution of
observations in one sample and a distribution of statistics
(sample means) from many samples (n greater than 1) that have been
randomly selected.
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II. What students should be able to DO with
this knowledge:
- Describe what a sampling distribution would
look like for different populations and sample sizes (in terms of
shape, center and spread, and where the majority of values would
be found). What values of the sample mean are likely, and which
are less likely.
- Describe the size of the standard error of the
mean
- Describe the likelihood of different values of
the sample mean
- Describe the mean of the sample means for
different shaped populations
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III. Some common misconceptions students should
NOT have:
- Sampling distribution should look like the
population (for n > 1)
- Sampling distributions for small and large
sample sizes have the same variability
- Sampling distributions for large samples have
more variability
- Don't understand that a sampling distribution
is a distribution of sample statistics
- Confuse one sample (real data) with all
possible samples (in distribution) or potential samples
- Representing a population (better for large
samples) is confused with a sampling distribution for large
samples, better representing a population (have more area)
- Students pay attention to the wrong things:
e.g., heights of bars
- The mean of a positive skewed distribution
will be greater than the mean of the sampling distribution for
samples taken from this population
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IV. Prerequisite knowledge students should have
before using the tools:
- The idea of a distribution
- What variability means (spread vs.
smoothness)
- The idea of the center of a distribution
- A random sample
- A sample statistic vs. a population
parameter
- Common shapes of distributions: normal,
skewed, uniform, bimodal
- Being able to see between the data, to
recognize overall shapes of distributions
- The idea of area under a curve and how it
represents likelihood of outcomes
- Properties of the normal distribution
- Normal distributions can look different due to
different variability (shape vs. variance)
- How to read and interpret histograms
- The idea of sampling variability
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