Review

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Review
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Normal Distribution
This distribution represent the scores of a
population or a large sample. We can calculate
the probability of getting any single score by
taking that score, subtracting the mean and
dividing by our measure of variability (middle
68)
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We convert this z to an area under the curve
which gives us probability.
We can see if this score is significantly
different from the mean. Compare Zobs (the z
you just calculated) to Zcrit (from the
summary table I gave you). If Zobs gt Zcrit,
you reject H0, and say the score is
significantly different from the population.
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Single Sample Stats When You Know ?
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• This measure of variability is the standard
  error, and we get it from the following formula...

You can now plug this term into your Z formula.
We dont change this Zobs to an area under the
curve. Instead, we compare it to Zcrit (from the
table I gave you). If the Zobs gt Zcrit ,
we reject H0.
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Single Sample Stats When You Dont Know ?
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We must estimate standard error based on sample
standard deviation.
You can now plug this term into your t formula.
If the tobs (the t you just calculated) gt
tcrit (from the book) you reject H0. Note, we
dont know the population standard deviation, but
we can estimate it using the following formula.
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Note, we dont actually use this estimate in
any calculations. We can, however, use it to
estimate standard error (Formula 10.7).