AP Stats guy Flashcards
What is Statistics?
The study of variability
What is variability?
Differences… how things differ. There is variability everywhere.. We all look
different, act different, have different preferences… Statisticians look at these
differences.
What are 2 branches of AP STATS?
Inferential and Descriptive
What are DESCRIPTIVE STATS?
Tell me what you got! Describe to me the data that you collected, use pictures or summaries like mean, median, range, etc…
What are INFERENTIAL STATS?
Look at your data, and use that to say stuff about the BIG PICTURE… like tasting soup… a little sample can tell you a lot about the big pot of soup (the population)
Compare Descriptive and Inferential
STATS
Descriptive explains you about the data that you have, inference uses that data you have to try to say something about an entire population….
What is data?
Any collected information. Generally each little measurement… Like, if it is a survey about liking porridge… the data might be “yes, yes, no, yes, yes” if it is the number of saltines someone can eat in 30 seconds, the data might be “3, 1, 2, 1, 4,3 , 3, 4”
What is a population?
the group you’re interested in. Sometimes it’s big, like “all teenagers in the US”
other times it is small, like “all AP Stats students in my school”
What is a sample?
A subset of a population, often taken to make inferences about the population.
We calculate statistics from samples
Compare population to sample
populations are generally large, and samples are small subsets of these
population. We take samples to make inferences about populations. We use
statistics to estimate parameters
Compare data to statistics
Data is each little bit of information collected from the subjects…. They are the INDIVIDUAL little things we collect… we summarize them by, for example, finding the mean of a group of data. If it is a sample, then we call that mean a “statistic” if
we have data from each member of population, then that mean is called a
“parameter”
Compare data to parameters
Data is each little bit of information collected from the subjects…. They are the INDIVIDUAL little things we collect… we summarize them by, for example, finding
the mean of a group of data. If it is a sample, then we call that mean a “statistic” if we have data from each member of population, then that mean is called a
“parameter”
What is a parameter?
A numerical summary of a population. Like a mean, median, range… of a
population
What is a statistic?
A numerical summary of a sample. Like a mean, median, range… of a sample.
What is the difference between a parameter and a statistic?
BOTH ARE A SINGLE NUMBER SUMMARIZING A LARGER GROUP OF NUMBERS…. But pppp parameters come from pppp populations… sss statistics come from ssss
statistics.
What is the difference between quantitative and categorical
variables?
Quantitative variables are numerical measures, like height and IQ. Categorical are categories, like eye color and music preference
What is the difference between quantitative and categorical data?
The data is the actual gathered measurements. So, if it is eye color, then the data would look like this “blue, brown, brown, brown, blue, green, blue, brown… etc.”
The data from categorical variables are usually words, often it is simpy “YES, YES, YES, NO, YES, NO” If it was weight, then the data would be quantitative like “125,
155, 223, 178, 222, etc..” The data from quantitative variables are numbers.
What is the difference between discrete and continuous variables?
Discrete can be counted, like “number of cars sold” they are generally integers
(you wouldn’t sell 9.3 cars), while continuous would be something like weight of a
mouse… 4.344 oz.
What is a quantitative variable?
Quantitative variables are numeric like: Height, age, number of cars sold, SAT
score
What is a categorical variable?
Qualitative variables are like categories: Blonde, Listens to Hip Hop, Female, yes,
no… etc.
What is meant by relative
frequency?
The PERCENT of time something comes up (frequency/total)
How do you find relative frequency?
just divide frequency by TOTAL….
What is meant by cumulative frequency?
ADD up the frequencies as you go. Suppose you are selling 25 pieces of candy. You sell 10 the first hour, 5 the second, 3 the third and 7 in the last hour, the cumulative frequency would be 10, 15, 18, 25
What is the difference between a bar chart and a histogram
bar charts are for categorical data (bars don't touch) and histograms are for quantitative data (bars touch)
What is the difference between a population mean and a sample mean?
population mean is the mean of a population, it is a parameter, sample mean is a mean of a sample, so it is a statistic. We use sample statistics to make inferences about population parameters.
What symbols do we use for population mean and sample mean?
Mu for population mean (parameter), x-bar ̅ for sample mean (statistic)
How can you think about the mean and median to remember the difference when looking at a histogram?
mean is balancing point of histogram, median splits the area of the histogram in
half.
What is the median?
the middlest number, it splits area in half (always in the POSITION (n+1)/2 )
What is the mode?
the most common, or the peaks of a histogram. We often use mode with
categorical data
When do we often use mode?
With categorical variables. For instance, to describe the average teenagers
preference, we often speak of what “most” students chose, which is the mode. It is also tells the number of bumps in a histogram for quantitative data (unimodal, bimodal, etc…)
Why don’t we always use the mean, we’ve been calculating it all of our
life ?
It is not RESILIENT, it is impacted by skewness and outliers
How are mean, median and mode positioned in a skewed left histogram?
goes in that order from left to right. Mean-median-mode
How are mean, median and mode positioned in a skewed right
histogram?
goes in the opposite order.. Mode-median-mean
