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58 Cards in this Set
- Front
- Back
Chapter 1Distinguish between population and sample, parameter and statisticGood sampling methods: simple random sample, collect in appropriate ways
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INfo
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Frequency distribution: summarizing dataGraphs designed to help understand dataCenter, variation, distribution, outliers, changing characteristics over time
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INfo
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Two measures of center used as tools for analyzing data.
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Mean and median
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The value at the cneter or middle of data set.
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Measure of center
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What is the mean
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the measure of center obtained by adding the values and dividing the total by the number of values.
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This letter in the equation is the sum of a set of values. All the values added at the top.
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E
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this letter is the variable usually used to represent the individual data values. usually added together
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x
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This letter represents the number of data values in a sample.
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n
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this number represents the number of data values in a population.
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N
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_ Ex
x= -------- n ___ x is pronounced ‘x-bar’ and denotes the mean of a set of sample values |
Mean of a sample values
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µ= --------
N µ is pronounced ‘mu’ and denotes the mean of all values in a population |
mean of all values in a population
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MEAN
T or F. Is relatively reliable, means of samples drawn from the same population don't vary as much as other measures of center. takes every data value into account |
True
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Disadvantages of MEAN
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Is sensitive to every data value, one extreme value can affect it dramatically, is not a resistant measure of center
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the middle value when the original data values are arranged in order of increasing (or decreasing) magnitude
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Median
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median is denoted by the ___ with a ___ mark over it called the x-tilde
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X squiggle
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why is the advantage of using Median as a center of measure?
True or False |
it is not affected by an extreme value - it is a resistant measure of the center
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How to find the median if the data value is odd?
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The exact middle of the list
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if the number of data values is even the median is found how?
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by computing the mean of th two middle numbers
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The value that occurs with the greatest frequency.
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Mode
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True of False
Data set can have one, more than one, or no mode |
True
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two data values occur with the same greatest frequency
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Bimodal
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more than two data values occur with the same greatest frequency
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Multimodal
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No data value is repeated
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No mode
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Mode is the only measure of central tendency that can be used with nominal data
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True
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Which is mode, bimodal and no mode?
a. 5.40 1.10 0.42 0.73 0.48 1.10 b. 27 27 27 55 55 55 88 88 99 c. 1 2 3 6 7 8 9 10 |
Mode
Bimodal no mode |
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the value midway between the maximum and minimum values in the original data set
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Midrange
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what is the midrange calculation
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Midrange=Max value + minimum Value/ 2
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Midrange is sensitive to extremes. Because it uses only the maximum and minimum values, so rarely used
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Info
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Redeeming features for midrange.
Very easy to compute reinforces that there are several ways to define the center avoids confusion with median |
info
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the value at the center or middle of a data set?
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Measure of center
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4 ways to figure measure of center
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Mean, median, mode, midrange
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The most important of all numerical measurements used to describe data, and it is what most people call an average
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Mean
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a data set is the measure of center that is the middle value when the original data values are arranged in order of increasing magnitude
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Median
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Never use the term average when referring to measure of center.. use the correct term such as mean or median
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Info
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Mode is the only measure of center that can be used with data at the nominal level of measurement
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True
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This measurement applies to data that consists of names, labels, or categories.
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Nominal level of measurement
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We use this rule for mean, median and mid-range
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Round off rule for measures of center
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What is the round-off rule for measures of center
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Carry one more decimal place than is present in the original set of values
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Nominal data is data such as labels, names, categories.. there is no point in statistics for these things
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info
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Assume that all sample values in each class are equal to the class midpoint
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Mean from a frequency distribution
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Mean from a frequency distribution
__ E(f*x) x= ---------- Ef |
Find the class midpoint, multiply the class midpoint by the frequency add the totals and divide by the sum of the frequency
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Frequency distribution yields an approximation of
- x because it is not based on the exact original list of sample values. |
Info
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A=4 points b=3 points c= 2 points d=1 point f= 0 points
I Took a 3 credit course got an A, 4 got an A, 3 got an b, 3 got a C and 1 got an F __ E(w*x) x=---------------- E(w) |
(3*4)+ (4*4)+(3*3)+(3*2)+(1*0)
________________________________ 3+4+3+3+1 |
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Distribution of data is symmetric if the left half of its histogram is roughly a mirror image of its right half
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symmetric
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Distribution of data is skewed if it is not symmetric and extends more to one side than the other
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skewed
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(also called negatively skewed) have a longer left tail, mean and median are to the left of the mode
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Skewed to the left
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(also called positively skewed) have a longer right tail, mean and median are to the right of the mode
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Skewed to the right
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The mean and median cannot always be used to identify the shape of the distribution.
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True
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The range of a set of data values is the difference between the maximum data value and the minimum data value.
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Example
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Range=
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Maximum value- minimum value
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Range is is very sensitive to extreme values; therefore not as useful as other measures of variation.
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Info
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Round off rule for measures of variation
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When rounding the value of a measure of variation, carry one more decimal place than is present in the original set of data.
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Round only the final answer, not values in the middle of a calculation.
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True
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a set of sample values, denoted by s, is a measure of variation of values about the mean.
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Standard deviation
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a measure of variation of all values from the mean.
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Standard deviation
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The value of the standard deviation s is usually positive.
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True
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The value of the standard deviation s can increase dramatically with the inclusion of one or more outliers (data values far away from all others).
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True
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The units of the standard deviation s are the same as the units of the original data values.
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True
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