Standards in this strand: - - - - - - - - - -
Key Ideas and Details: -

With prompting and support, ask and answer questions about key details in a text. -

With prompting and support, identify the main topic and retell key details of a text. -

With prompting and support, describe the connection between two individuals, events, ideas, or pieces of information in a text.
Craft and Structure: -

With prompting and support, ask and answer questions about unknown words in a text. -

Identify the front cover, back cover, and title page of a book. -

Name the author and illustrator of a text and define the role of each in presenting the ideas or information in a text.
Integration of Knowledge and Ideas: -

With prompting and support, describe the relationship between illustrations and the text in which they appear (., what person, place, thing, or idea in the text an illustration depicts). -

With prompting and support, identify the reasons an author gives to support points in a text. -

With prompting and support, identify basic similarities in and differences between two texts on the same topic (., in illustrations, descriptions, or procedures).
Range of Reading and Level of Text Complexity: -

Actively engage in group reading activities with purpose and understanding.

If 50% of all the people in a population of 20000 people drink coffee in the morning,
and if you were repeat the survey of 377 people ("Did you drink coffee this morning?")
many times, then 95% of the time, your survey would find that between 45% and 55% of
the people in your sample answered "Yes".
The remaining 5% of the time, or for 1 in 20 survey questions, you would expect the
survey response to more than the margin of error away from the true answer.
When you
survey a sample of the population, you don't know that you've found the correct
answer, but you do know that there's a 95% chance that you're within the margin of
error of the correct answer.
Try changing your sample size and watch what happens to the * alternate scenarios* .
That tells you what happens if you don't use the recommended sample size, and how and confidence level (that 95%) are related.
To learn more if you're a beginner, read Basic
Statistics: A Modern Approach and
The Cartoon Guide to Statistics . Otherwise, look at the
more advanced books .

In terms of the numbers you selected above, the sample size * n* and margin of error
* E* are given by
* x* = * Z* ( * c* / 100 ) 2 * r* (100-* r* )
* n* =
* N x* / ((* N* -1)* E* 2 + * x* )
* E* = Sqrt[ (* N* - * n* )* x* / * n* (* N* -1) ]
where * N* is the population size, * r* is the fraction of
responses that you are interested in, and * Z* (* c* /100) is
the critical
value for the confidence level * c* .

If you'd like to see how we perform the calculation, view the page
source. This calculation is based on the Normal
distribution , and assumes you have more than about 30 samples.

About Response distribution : If you ask a random sample of
10 people if they like donuts, and 9 of them say, "Yes", then the
prediction that you make about the general population is different than it
would be if 5 had said, "Yes", and 5 had said, "No". Setting the response
distribution to 50% is the most conservative assumption. So just leave it
at 50% unless you know what you're doing.
The sample size calculator computes the critical value for the normal
distribution. Wikipedia has good articles on statistics.
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