What is Statistics?

the study of variability

What are the two 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)

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.

what is a parameter?

A numerical summary of a population. Like a mean, median, range? of a population

what is a Statisitc?

A numerical summary of a sample. Like a mean, median, range? of a sample.

Compare DATA-STATISTIC-PARAMETER using categorical example

Data are individual measures? like meal preference: ?taco, taco, pasta, taco, burger, burger, taco?? Statistics and Parameters are summaries. A statistic would be ?42% of sample preferred tacos? and a parameter would be ?42% of population preferred tacos.?

Compare DATA-STATISTIC-PARAMETER using quantitative example

Data are individual measures, like how long a person can hold their breath: ?45 sec, 64 sec, 32 sec, 68 sec.? That is the raw data. Statistics and parameters are summaries like ?the average breath holding time in the sample was 52.4 seconds? and a parameter would be ?the average breath holding time in the population was 52.4 seconds?

what is a census?

Like a sample of the entire population, you get information from every member of the population

does a census make sense?

A census is ok for small populations (like Mrs. Buckley’s students) but impossible if you want to survey “all US teens”

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 samples.

If I take a random sample of 20 hamburgers from FIVE GUYS and count the number of pickles on a bunch of them? and one of them had 9 pickles, then the number 9 from that burger would be called ____?

a datum, or a data value.

If I take a random sample 20 hamburgers from FIVE GUYS and count the number of pickles on a bunch of them? and the average number of pickles was 9.5, then 9.5 is considered a _______?

statistic. (t is a summary of a sample.)

If I take a random sample of 20 hamburgers from FIVE GUYS and count the number of pickles on a bunch of them? and I do this because I want to know the true average number of pickles on a burger at FIVE GUYS, the true average number of pickles is considered a ______?

parameter, a one number summary of the population. The truth. AKA the parameter of interest.

What is the difference between a sample and a census?

With a sample, you get information from a small part of the population. In a census, you get info from the entire population. You can get a parameter from a census, but only a statistic from a sample.

What are random variables?

If you randomly choose people from a list, then their hair color, height, weight and any other data collected from them can be considered random variables.

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 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 quantitative data?

The actual numbers gathered from each subject. 211 pounds. 67 beats per minute.

What is a random sample?

When you choose a sample by rolling dice, choosing names from a hat, or other REAL RANDOMLY generated sample. Humans can’t really do this well without the help of a calculator, cards, dice, or slips of paper.

What is frequency?

How often something comes up

What is a frequency distribution?

A table, or a chart, that shows how often certain values or categories occur in a data set.

What is meant by relative frequency?

The PERCENT of time something comes up (frequency/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 mean?

the old average we used to calculate. It is the balancing point of the histogram

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.

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 )

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