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Unformatted text preview: pulation proportion either by
name or by formula (numbers plugged in is OK);
• checks to make sure that the sample size is large enough; and
• and has correct computations (.3602, .4198)
Partially correct if just one of the above is incorrect or missing.
2. Interpretation of the confidence interval is
Essentially correct if it is clear, correct, and in context (include the numbers).
Partially correct if unclear or no context is given.
Incorrect if it says “The probability or chance that the true proportion is between .36 and
.42 is .95,” or if it looks like the sample proportion is in the confidence interval [“…the
proportion of U.S. adults who said…” (past tense)].
OK to say “95 percent sure.”
3. Interpretation of the confidence level is
Essentially correct if it is clear and correct (no context needed).
Partially correct if it is somewhat unclear but nothing is clearly incorrect.
Incorrect if it says “In 95 of every 100 samples, the population proportion will be
between .36 and .52,” or “will be in this interval.”
4. Answer to (b) may be scored essen...
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