You are studying the measurement of a new biomarker for
cardiovascular disease, and how it might be applied to general
practice. You assume that the data for this particular biomarker
are likely to be normally distributed.

When considering the normal distribution, which of the following
is true?

A.95% of observations lie within the mean and 1 standard deviation B.Data need to be transformed before they can be analysed with
parametric tests C.Data with a tail of values which is greater than the upper end of
the distribution are normally distributed D.The mean, median and mode are the same value E.The 95% confidence interval tells us how confident we are in the test

[正确答案]： D

The mean and median and mode of a normal distribution are equal,
because the distribution curve of a normal distribution is bell
shaped and equal on both sides.

The probability that a normally distributed random variable x,
with mean sigma, and standard deviation µ, lies between (sigma -
1.96 µ) and (sigma + 1.96 µ) is 0.95.

The probability that a normally distributed random variable x,
with mean sigma, and standard deviation µ, lies between (sigma - µ)
and (sigma + µ) is 0.68.

Ninety five per cent of the distribution of sample means lie
within 1.96 standard deviations of the population mean.

A parametric test is a statistical test which assumes the data
are normally distributed.

Data which are not normally distributed can still be subject to
a parametric test, but it need to be transformed first.