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29 Cards in this Set
- Front
- Back
What is Descriptive statistics ? |
Methods used to summarize or describe the important characteristics of a set of data. |
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What is Inferential Statistics ? |
Methods that use sample data to make inferences about the population. |
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Five important characteristics about data ? CVDOT |
Center Variation Distribution Outliers Time |
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What is a frequency distribution |
Shows how a data set is distributed by listing all the classes or categories and the number of values in each. |
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List 5 important characteristics about Frequency tables |
Lower class limits upper class limits class midpoints class boundaries class width
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List 3 reasons for constructing frequency distributions |
Large data sets can be summarized We can analyze the nature of data We have a basis for constructing important graphs |
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Steps to constructing a frequency table |
1) # classes 2)Determine the class width- (max - min ) / # classes 3) List the first lower class limits , then all the others, then the upper class limits , then tally . |
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What is relative frequency and percentage frequency . |
Relative frequency - class frequency / sum of all frequencies Percentage frequencies - class frequency /sum of all frequencies x 100 |
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List 3 characteristics of a Histogram |
1-A graph consisting of bars of equal width drawn adjacent to each other 2-The horizontal scale represents the classes 3-The vertical scale represents frequencies |
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What does the horizontal scale for a histogram use ? What does the vertical scale for a histogram use ? |
Horizontal scale can use - class boundaries,class midpoints, lower class limits (introduces small errors) Vertical scale uses - class frequencies |
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List 5 types of graphs |
Scatterplot, dot plot, stem plot, multiple bar graph , bar graph |
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List the four measure of center |
Mean, median, mode, midrange (max+min)/2 |
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What is advantage and disadvantage of the mean ? |
Advantage- Takes every data into account , Disadvantage - Is sensitive to every data value, sensitive to extreme values , not resistant measure of center |
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What is the advantages and disadvantages of Median ? |
Advantages - not affected by extreme values, is a resistant measure of the center Disadvantages - Does not take every value into account |
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What is the advantage and disadvantages of the Mode And one interesting fact |
Advantage - Not affected by extreme values Disadvantage - Does not take every value into account can be used for nominal data can have more than 1 mode |
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What are the advantages and disadvantages of the Midrange ? |
Advantages - Very easy to compute, Disadvantages - Sensitive to extremes |
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What is the round-off rule for measures of center |
Carry one more decimal place than is present in the original set of values. |
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Remember, mean from a frequency distribution |
Sum of frequency by x(class midpoint) over the sum of frequency |
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What is weighted mean ? |
sum of weight by x over sum of weight |
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Remember skewed and symmetric data |
s |
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Skewed to the left and skewed to the right ? |
Skewed to the left (negatively skewed)- a longer tail to the left, the mean and median are to the left of the mode Skewed to the right(positively skewed)- a longer tail to the right, the mean and median are to the right of the mode. |
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What is the range ? |
difference between the maximum and minimum values Very sensitive to extreme values, therefore its not as useful as other measures of variation. |
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What is the round-off rule for Measures of Variation |
Round only the final answer Carry one more decimal place than is present in the original set data . |
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What is standard deviation ? |
s - measure of variation of values about the mean. The value is usually positive The value can increase dramatically with the inclusion of one or more outliers The units of standard deviation are the same as the units of the original data values |
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Rules for comparing 2 standard deviations and 2 variations ? |
1) Compare 2 standard deviations only when the sample means are approximately the same. 2) When Comparing variations in sample with very different means its best to use the coefficient of variation . |
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What is the range rule of thumb ? |
95% of sample values lie within two standard deviations of the mean |
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What is Empirical Rule ( 68-95-99.7) ? |
1) 68% of all values fall within 1 standard deviation of the mean 2) 95% 3) 99.7% of all values fall within 3 standard deviation of the mean |
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What is the coefficient of variation (CV) |
standard deviation over mean by 100 |
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What is the z score ? |
The number of standard deviation that a given value x is above or below the mean |