CH 3 Describing, Exploring and Comparing Data
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What term is a value at the center or middle of a data set?
Measure of center
What set of data is the measure of center found by adding all the data values and dividing the total by the number of data values?
Mean or arithmetic mean
What term describes a statistic that, in the presence of extreme values, it does not change very much?
resistant
What are some disadvantages of mean?
is is not resistant an extreme value can change the value substantially
What is the formula for mean?
What is the formula for the mean of a set of sample values?
What is the fromula for the mean of all values in a population?
What data set is the measure of center that is the middle value when the original data values are arranged in order of increasing (or decreasing) magnitude?
median
How do you find the median?
sort values in order if the number of data values is odd, the median is the number located in the center if the number of data values is even, the median found by computing the mean of the two middle numbers
What data set is the value(s) that occur with the greatest frequency?
mode
What type of data is mode used with?
qualitative data (names, labels, categories)
When calculating the mode, how would you describe the data if two values occured with the same greatest frequency?
bimodal mulitmodal - more than two
What is the measure of center that is the value midway between the maximum and minimum values in the original data set?
midrange
How do you calculate the midrange of a data set?
Midrange = (max data value + min data value) / 2
What are the round-off rules for measures of center?
for the mean, median and midrange, carry one more decimal place than is present in the original set of values for the mode, leave the value as is without rounding
What is the formula used to caluculate mean from a frequency distribution?
What is the formula for calculating weighted mean?
What set of data values is the differnece between the maximum data value and the minimum data value?
range
What is a measure of how much data values deviate away from the mean?
standard deviation
What is the formula for sample standard deviation?
List the steps for for finding the standard deviation of the following: 84 74 50 60 52
• Compute the mean (64) • Subtract the mean from each (20 10 -14 -4 -12) • Square each dviation obtained from the previous step • Add all the squars obtained • Divide total by n-1 • Find the square root of the results
What is the Range Rule of Thumb for Estimating a Value of the Standard Deviation?
What is the symbol for the mean of a sample and a population?
What is the formula for finding the standard deviation of a population?
