12.4 The Normal Distribution

percentile

If n% of the items in a distribution are less than a particular data item, we say that the data item is in the nth ______________ of distribution.

normal distirbution

In a _______________, approximately 68 % of the data items fall within 1 standard deviation of the mean, approximately 95% of the data items fall within 2 standard deviation of the mean, and approximately 99.7% of the data items fall within 3 standard deviations of the mean.

true

True or False: A score in the 50th percentile on a standardized test is the median.

false

True or False: The z-score for a data item in a normal distribution is obtained using z-score = (data item-standard deviation)/mean.

mean

A z-score describes how many standard deviations a data item in a normal distribution lies above or below the _______________.

margin of error

If a statistic is obtained from a random sample of size n, there is a 95% probability that it lies within (1/√n)×100% of the true population percent, where ±(1/√n)×100% is called the ____________.

false

True or False: In a distribution, the z-score for the mean is 1.

true

True or False: The mean, median, and mode of a normal distribution are all equal.