Stats TEST 1 PREP
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what are the 2 types of data?
What is Categorical data?
Data made up of categories (not numbers) with "usual meaning
How do you compute Relative Frequency?
Frequency divided by total
What is Statistics?
Science of using data to analyze questions of interest and draw conclusions.
What is the experimental unit?
It is the object which you are studying
What is the experimental unit if you're studying the GPA of students?
Each individual student
What is a population in statistics?..give example.
- A collection of all experimental units of interest
- Ex: an entire student body
What is a statistical census?
This is a method for finding attributes of all members of a statistical population of interest
What is a statistical sample?
A subset of an entire population
What are the 3 major branches of statistics?
What is Descriptive Statistics?
Utilizes techniques to describe attributes of data sets
What is Probability Statistics?
This tells us what sorts of inferences we can make about a population based on the sample
What is Inferential Statistics?
Drawing conclusions from a sample that might be applicable to the whole population
What is a statistical variable?
A characteristic of the experimental unit of interest
What are the 2 types of variables?
Categorical and Quantitative
What is a quantitative variable?..and give an example.
- Variable that has natural ordering and are numeric
- Ex: Money
What is a discrete quantitative variable and give an example.
- This is a quantitative variable that can only take discrete numerical values?
- Ex: Integers
What is a continuous quantitative variable..example?
- This is a variable that can take on any numerical value
- Ex: All Real #s
If a variable is bounded, can it not qualify as continuous..exxample?
- No. A variable can be bounded and still be continuous.
- Ex: Non-negative #s
Found by adding up all of our data and dividing
by number of data points
If a statistical attribute (ex: mean) changes a lot when we change large values and changes little when we change little values then it is:
Is mean a resistant statistical attribute?
What is median?
The middle value when a set of sample #s are ordered numerically
If a statistical attribute (ex: median) doesn't change at all when a new value is introduced to it then it is...
If you have an even number of values, how do you find their median when ordered numerically?
the median is the mean of the middle 2 values in the order.
If the mean is roughly equal to the median, what shape would you expect your data set to be?
What cane you say about the shape of the data if the mean is greater or less than the median?
If mean is greater then positive skewed; if less than the median then it is negatively skewed
What is the mode?
The value that appears most often
This is specifically the equation for...
Sample Standard deviation
This is the formula for...
And what does Mu stand for in this?
- Population Standard Deviation
- Mu is population mean
This is the formula for
Sample Variance (Standard Deviation squared)
What are Q1, Q2, and Q3 for IQR?
- Q1=Median of 1st half of data set
- Q2= median of full set
- Q3= Median of 2nd half of set
Are the quartiles in IQR and the IQR itself resistant?
If you have an odd number of data, what do you do with the middle value when calculating quartiles?
The middle value is included in both Q1 and Q3 calculations.
Name the resistant measures of spread and center
Name the non-resistant measures of spread and center
How do you designate the range in which a value is considered and outlier?
- If it is less than Q1-1.5*IQR
- If it is greater than Q3+1.5*IQR
When can you drop and observation from a data set?
- When you are certain of it being a mistake
- When you know the observation came from the wrong population
What does the Empirical rule say about data?
68% of data falls within the first standard deviation, 95% falls within the second standard deviation, and 99.7% of the data falls within 3 standard deviations
What are the characteristics of bell-shaped data?
- mean and median are relatively close to each other
How do you calculate statistical density?
- Density = Relative Frequency divided by group
What are some topics you should include when summarizing a set of data
What is the easiest way to find the skewness of a set of data?
- Find the mean and compare it to the median
- If the mean is greater than the median then you have positive skew
- If mean is less than median then negative skew
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