Chapter 1 Flashcards
What are the two criteria for a random sample?
- Equal chance of being selected
2. Independent of each other
Explanatory variable
Independent variable
Predictor variable
Always on the x axis
Response variable
Dependent variable. What is being measured ? What do we want to predict ? Always on the y axis
Frequency distribution
Number of times each value of a variable occurs in a sample
What is the criteria for a good sample?
Minimizing sampling error (precision ) Minimizing bias (accuracy)
Explanatory variable
Predictor variable
What 4 things do you look for when interpreting histograms?
Over all pattern?
What is the shape?
What is the spread?
Any striking deviations?
Graph to make with 2 categorical variables
Grouped bar graph
Graph to make with one categorical and one numerical variable
Bar graph
What does standard deviation measure ?
Measure of how different values are from the mean
How is standard deviation calculated ?
The square root of variance
What is coefficient of variation ?
Expresses the standard deviation as a percentage of the mean
What happens when the coefficient of variation increases ?
There is more variability
What is IQR ? How is it calculated ?
Inter quartile range = difference between the first and third quartile.
Which measurement methods are more sensitive to extremes?
Standard deviation and mean !
What three things describe the shape of a distribution ?
Symmetric or asymmetric ?
Center of data ?
Spread of data ?
What spread measurement is associated with median?
Inter quartile range
How do outliers affect mean? Median?
Mean increases
Median remains unchanged !
How does the mean relate to the median if the data is left skewed ?
Mean is larger than the median
How are mean and median related when the spread is symmetrical ?
Mean = median
What measure of location should be used if the distribution is symmetrical ?
Mean
What part of the box plot represents the IQR ?
The entire box
What will a box plot look like if it is left skewed ?
Median line is closer to the top of the box
What will a box plot look like if it is right skewed ?
The median line is closer to the bottom of the box
Explanatory variable
Predictor variable
What 4 things do you look for when interpreting histograms?
Over all pattern?
What is the shape?
What is the spread?
Any striking deviations?
Graph to make with 2 categorical variables
Grouped bar graph
Graph to make with one categorical and one numerical variable
Bar graph
What does standard deviation measure ?
Measure of how different values are from the mean
How is standard deviation calculated ?
The square root of variance
What is coefficient of variation ?
Expresses the standard deviation as a percentage of the mean
What happens when the coefficient of variation increases ?
There is more variability
What is IQR ? How is it calculated ?
Inter quartile range = difference between the first and third quartile.
Which measurement methods are more sensitive to extremes?
Standard deviation and mean !
What three things describe the shape of a distribution ?
Symmetric or asymmetric ?
Center of data ?
Spread of data ?
What spread measurement is associated with median?
Inter quartile range
How do outliers affect mean? Median?
Mean increases
Median remains unchanged !
How does the mean relate to the median if the data is left skewed ?
Mean is larger than the median
How are mean and median related when the spread is symmetrical ?
Mean = median
What measure of location should be used if the distribution is symmetrical ?
Mean
What part of the box plot represents the IQR ?
The entire box
What will a box plot look like if it is left skewed ?
Median line is closer to the top of the box
What will a box plot look like if it is right skewed ?
The median line is closer to the bottom of the box
What causes outliers?
Natural variation
Human error in recording
Human error in experimentation
What is the observational unit ?
The subject that is being tested on
How does the sample size affect a sampling distribution ?
If the sample size is increased then there will be less variation in the sample distribution. Precision is increased
What does sampling distribution measure ?
Precision of an estimate
What happens to the standard error of the mean as the sample size increases ?
As the sample size increases the standard error of the mean decreases
Formula for SE?
S/ (square root of n)
What does standard error describe?
The spread of the distribution of the sample means. Aka precision.
What happens to standard deviation as sample size increases ?
The sd becomes more
Precise
Name two measures of uncertainty
Confidence interval and standard error of the mean
What is the unit of replication ?
Wherever the treatment is applied
What does the confidence interval do ?
Quantifies the uncertainty about values
