Musuq
Forum Guru
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Serum LDL-cholesterol concentrations are measured in blood samples collected from 100 healthy volunteers. The data follow a normal distribution. The mean and standard deviation for this group is 130 mg/dL and 20 mg/dL, respectively. The standard error of the mean is 5.0. The 95% confidence interval about the mean is 120 to 140 mg/dL. If blood samples are collected from 25 healthy volunteers instead of 100, which of the following best expresses the expected impact on the standard error and the 95% confidence interval about the mean?
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| smal
Forum Guru
Topics: 140
Posts: 727
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guys,they say mean is 130 and SD is 20. that would make SEM as 20/10.i.e.2 rt?
but in the next line they give SEM is 5.!(couldnt follow-or they want us to use the data for calculating SEM for the next case only,but that doesnt justify the situation)
so confidence interval =mean+1.96(SD/N under root)
technically speaking should increase,so E.
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| NE
Forum Guru
Topics: 53
Posts: 504
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It is E- the real question is what is going to happen if the sample decreases.
CI= mean+/- SE, so they increase/ decrease proportionaly.
SE= S/N ( radical) so if the sample decreases the SE increases.
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| NE
Forum Guru
Topics: 53
Posts: 504
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I forgot about the Z but in this q doesn't matter.
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| MD_toronto
Forum Junior
Topics: 2
Posts: 27
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E
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