Example: Awe…Nuts! - Village Christian School
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Transcript Example: Awe…Nuts! - Village Christian School
How many movies do you watch?
Does the CLT apply to means?
The Central Limit Theorem states that the more
samples you take, the more Normal your graph will
appear for either the sample mean or sample
proportion.
What do we need to verify in order to say the
distribution should be approximately normal?
Independence Assumption:
• In order to be able to consider each sample an
unbiased estimator, we must insure that random
selection was used.
• If we want to insure we aren’t affecting the probability
of selecting each sample, we must insure that the
sample we take is less then 10% of our population.
Does the CLT apply to means?
Back to the show…
Back to the show…
Suppose that the number of movies viewed in the last
year by all high school students in CA has an average of
19.3 and a standard deviation of 15.8 . If we were to
randomly sample 100 high school students many times,
what would we expect the average of the sampling
distribution to be? What about the standard deviation?
Independence Assumption:
We are given that the selection would be random. We
can also safely assume that there are more then 1,000 high
school students in CA.
Large Enough Condition:
Since n = 100 > 30 we can state that the distribution
would be approximately Normal.
Example: Awe…Nuts!
At the P. Nutty Peanut Co., dry-roasted, shelled peanuts are
placed in jars by a machine. The distribution of the weights in
the jars is approximately Normal with a mean of 16.1 oz and a
standard deviation of .15 oz.
Without doing any calculations, explain which
outcome is more likely: randomly selecting a
single jar and finding that it weighs less than 16
oz. or randomly selecting 10 jars and finding that
the average is less than 16 oz.?
Find the probability of each of these events.
Example: Awe…Nuts!
At the P. Nutty Peanut Co., dry-roasted, shelled peanuts are
placed in jars by a machine. The distribution of the weights in
the jars is approximately Normal with a mean of 16.1 oz and a
standard deviation of .15 oz.
Without doing any calculations, explain which
outcome is more likely: randomly selecting a
single jar and finding that it weighs less than 16
oz. or randomly selecting 10 jars and finding that
the average is less than 16 oz.?
Follow the 4 Step Process!
1. State what you want to know:
We want to find the probability of selecting a
single jar that weighs less then 16 oz.
Example: Awe…Nuts!
At the P. Nutty Peanut Co., dry-roasted, shelled peanuts are
placed in jars by a machine. The distribution of the weights in
the jars is approximately Normal with a mean of 16.1 oz and a
standard deviation of .15 oz.
Without doing any calculations, explain which
outcome is more likely: randomly selecting a
single jar and finding that it weighs less than 16
oz. or randomly selecting 10 jars and finding that
the average is less than 16 oz.?
Step 2: Verify Your Assumptions
Independence Assumption:
We are told that the jar is randomly selected. And we can
assume that on any given day the P. Nutty Company makes
more then 10 jars of peanuts.
Example: Awe…Nuts!
At the P. Nutty Peanut Co., dry-roasted, shelled peanuts are
placed in jars by a machine. The distribution of the weights in
the jars is approximately Normal with a mean of 16.1 oz and a
standard deviation of .15 oz.
Without doing any calculations, explain which
outcome is more likely: randomly selecting a
single jar and finding that it weighs less than 16
oz. or randomly selecting 10 jars and finding that
the average is less than 16 oz.?
Step 2: Verify Your Assumptions
Large Enough Condition:
Since we are given that the distribution of weights is
approximately Normal, even though our sample is small, it is
safe to proceed.
Example: Awe…Nuts!
Example: Awe…Nuts!
This makes sense, because if the
distribution is approximately
Normal. Then the mean would
divide the distribution in half.
Example: Awe…Nuts!
At the P. Nutty Peanut Co., dry-roasted, shelled peanuts are
placed in jars by a machine. The distribution of the weights in
the jars is approximately Normal with a mean of 16.1 oz and a
standard deviation of .15 oz.
Without doing any calculations, explain which
outcome is more likely: randomly selecting a
single jar and finding that it weighs less than 16
oz. or randomly selecting 10 jars and finding that
the average is less than 16 oz.?
In your notes, follow the 4 step process to solve
this problem. I will randomly select students to
come up to the board and show their work.