Biostats Chapter 2

Front 1

What is Descriptive statistics ?

Back 1

Methods used to summarize or describe the important characteristics of a set of data.

Front 2

What is Inferential Statistics ?

Back 2

Methods that use sample data to make inferences about the population.

Front 3

Five important characteristics about data ?

CVDOT

Back 3

Center

Variation

Distribution

Outliers

Time

Front 4

What is a frequency distribution

Back 4

Shows how a data set is distributed by listing all the classes or categories and the number of values in each.

Front 5

List 5 important characteristics about Frequency tables

Back 5

Lower class limits

upper class limits

class midpoints

class boundaries

class width

Front 6

List 3 reasons for constructing frequency distributions

Back 6

Large data sets can be summarized

We can analyze the nature of data

We have a basis for constructing important graphs

Front 7

Steps to constructing a frequency table

Back 7

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 .

Front 8

What is relative frequency and percentage frequency .

Back 8

Relative frequency - class frequency / sum of all frequencies

Percentage frequencies - class frequency /sum of all frequencies x 100

Front 9

List 3 characteristics of a Histogram

Back 9

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

Front 10

What does the horizontal scale for a histogram use ?

What does the vertical scale for a histogram use ?

Back 10

Horizontal scale can use - class boundaries,class midpoints, lower class limits (introduces small errors)

Vertical scale uses - class frequencies

Front 11

List 5 types of graphs

Back 11

Scatterplot, dot plot, stem plot, multiple bar graph , bar graph

Front 12

List the four measure of center

Back 12

Mean, median, mode, midrange (max+min)/2

Front 13

What is advantage and disadvantage of the mean ?

Back 13

Advantage- Takes every data into account ,

Disadvantage - Is sensitive to every data value, sensitive to extreme values , not resistant measure of center

Front 14

What is the advantages and disadvantages of Median ?

Back 14

Advantages - not affected by extreme values, is a resistant measure of the center

Disadvantages - Does not take every value into account

Front 15

What is the advantage and disadvantages of the Mode

And one interesting fact

Back 15

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

Front 16

What are the advantages and disadvantages of the Midrange ?

Back 16

Advantages - Very easy to compute,

Disadvantages - Sensitive to extremes

Front 17

What is the round-off rule for measures of center

Back 17

Carry one more decimal place than is present in the original set of values.

Front 18

Remember, mean from a frequency distribution

Back 18

Sum of frequency by x(class midpoint) over the sum of frequency

Front 19

What is weighted mean ?

Back 19

sum of weight by x over sum of weight

Front 20

Remember skewed and symmetric data

Back 20

s

Front 21

Skewed to the left and skewed to the right ?

Back 21

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.

Front 22

What is the range ?

Back 22

difference between the maximum and minimum values

Very sensitive to extreme values, therefore its not as useful as other measures of variation.

Front 23

What is the round-off rule for Measures of Variation

Back 23

Round only the final answer

Carry one more decimal place than is present in the original set data .

Front 24

What is standard deviation ?

Back 24

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

Front 25

Rules for comparing 2 standard deviations and 2 variations ?

Back 25

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 .

Front 26

What is the range rule of thumb ?

Back 26

95% of sample values lie within two standard deviations of the mean

Front 27

What is Empirical Rule ( 68-95-99.7) ?

Back 27

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

Front 28

What is the coefficient of variation (CV)

Back 28

standard deviation over mean by 100

Front 29

What is the z score ?

Back 29

The number of standard deviation that a given value x is above or below the mean