Exam II Lecture 11 Stats 2 Flashcards
Disadvantage of measuring the mean.
Is sensitive to every data value, one extreme value can affect it dramatically; is not a resistant measure of center
Difference between a median and mean.
Modes are the middle value arranged in order from low to high.
The key is, unlike the mean, median is not affected by extreme values.
Mode
Value that occurs with the greatest frequency.
The only measure of center that can be used with nominal data
mode
What is the range sensitive to?
Extreme values and is not useful as other measures of variation.
Variance
Set of values equal to the square of the standard deviation.
Z score
The number of standard deviations that a given value x is above or below the mean.
The mean of the z scores of a population is always…
0
The standard deviation of teh z scores of a population is always….
1
Normal value for Z score?
less than a difference of +2 or -2
Probability sample
Selecting members from population in such a way that they al have a known chance of being selected.
Random sampling
Selection so that each individual member has an equal chance of being selected.
Simple random sample
of n subjectes selected in such a way that every possible sample of the same size n has the same chance of being chosen.
Systematic sampling
select some starting point and then select every kth element in the population.
stratified samping
subdivide the population into at least two different subgroupsthat share teh same characteristics, then draw a sample from each subgroup or stratum.
