Flashcards in Stat - Exam #1 Deck (134)

Loading flashcards...

31

## Why can’t observational studies determine causation?

###
-Because of possible lurking variables;

-Lurking = No measure, but DO affect the results (EX: Snoring and a risk of heart attack)

32

## What does an experiment mean in statistics?

###
-High level of control;

-Often takes more than one study to eliminate or control lucking variables

33

## What is an Experimental Unit?

### An individual in a sample

34

## What is Treatment?

### A A condition of interest that is applied to the experimental unit

35

## What is the Response Variable?

### A quantitative or qualitative variable that reflects the characteristic of interest

36

## What is a Double Blind study?

### Neither the researcher nor the experimental unit knows whether, or what, treatment is being applied

37

## What is a Placebo?

###
-A false treatment that has NO effect;

-Used to prevent experimental units from knowing whether they are being treated

38

## How do I describe a column of data?

###
Distribution of data gives SHAPE, LOCATION, and SPREAD;

-These are very useful in abstracting the info from the data

39

## What is the process of statistics?

###
1. Ask question;

2. Collect data = census, observational study, experimental design, or existing data;

3. Organize and analyze = overview with tables/graphs; detailed using methods depending on type;

4. Make a conclusion

40

## What is Raw Data?

### Data NOT organized

41

## How is a variable (column of data) described?

###
-Condense and described by distribution;

-Distribution described by shape, location, and spread =

— Graphical methods determine shape;

— Numerical methods find location and spread

42

## How can Qualitative data be graphically summarized?

###
-Frequency table and in a Graph (bar chart, pareto chart, and pie chart);

-Frequency organizes = shows what possible VALUES a variable take and HOW OFTEN each value;

-Picture give better overview

43

## What is Frequency Table?

###
A table that lists all categories of data, with number of occurrences for each category;

-5 Columns =

1. Category

2. Frequency

3. Relative Frequency

4. Cumulative Frequency

5. Cumulative Relative Frequency

44

## What is Category?

### Lists the names of all categories in a column of data

45

## What is Frequency?

### The number of observations in each category

46

## What is Relative Frequency?

###
The percent, or proportion, of data in each category;

Relative Frequency = (Frequency/Sum of all Frequencies)

47

## What is Cumulative Frequency?

###
The sum of frequency up through, and including category of interest;

-the number of observations less than or equal to the category value

48

## What is Cumulative Relative Frequency?

### The sum of relative frequency up through and including the category of interest

49

## What is a Bar Chart?

###
A graph of a set of data made with:

1. Categories on horizontal axis

2. Frequencies on vertical axis;

3. Rectangle of equal width (bar) drawn for each category with the hight equal to the category’s frequency (or relative frequency);

-Bars do NOT touch;

- Value are in the middle of the bars

50

## What is a Pareto Chart?

### A bar chart whose bars are drawn in descending order of height

51

## What is a Pie Chart?

###
A circle divided in to wedges, where each wedge represents a category and the size of the wedge represents the relative frequency of a category;

-Summarizes qualitative data

52

## How is Discrete Data summarized?

###
-HISTOGRAM;

-Values are used to create categories;

-Histogram bar DO touch;

-Values marked in the middle of the bars

53

## How do you graphically represent Continuous Data?

###
-Too many categories since each number is its own category;

-To condense, need to GROUP data into intervals and create new, smaller categories;

1. Group into classes; make a frequency table; make a histogram;

2. Or make a stem-and-leaf plot

54

## What is the method to group Continuous data into classes?

###
1. Decide on the number of intervals (5-20).

2. Find the width of each interval (divide range by number of intervals)

3. Select a starting point for the first interval (usually the min)

4. Make the remaining intervals equidistant from start = equal widths, adjacent, no overlap, and convenient endpoints

55

## What is a Histogram for CONTINUOUS data?

###
-Graph of a set of data made like a bar chart, but:

1. Bars DO touch;

2. The lower limit of each class is marked at the LEFT of each rectangle

56

## What is a Stem-and-Leaf Plot?

### -Graph to summarize continous data by dividing each data point into a star and and a leaf part and listing these parts

57

## What is the method to make a Stem-and-Leaf Plot?

###
1. Rank the data from low to high;

2. Divide each point into stem and leaf;

-Leaf = rightmost digit

-Stem = digits to the left of leaf;

3. Write stems vertically from low to high;

4. Draw line to right of numbers;

5. Write the leaf next to the corresponding stem

58

## How are distribution SHAPES described?

###
-Symmetric

-Skewed left

-Skewed right

-Uniform

-Bimodal

59

## How are histograms analyzed?

###
1. Overall shape (frequency curve);

2. Any deviation from general shape

60