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Stat 210 > Test 2 > Flashcards

Test 2 Flashcards

1
Q

What is Descriptive Statistics?

A

The branch of statistics concerned with numerical and graphical techniques for analyzing and describing one or more characteristics among populations.

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2
Q

When describing a Distribution what are the 4 things we use to describe them?

A
  1. The CENTER of the distribution
  2. The SPREAD (OR RANGE) of the distribution.
  3. The SHAPE of the distribution
  4. any UNUSUAL FEATURES (OUTLIERS) in the distribution
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3
Q

What is the purpose of Graphical Procedures?

A
  1. Simplify the data
  2. Make it easy to describe distributions
  3. Make it easy to make statistical inferences.
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4
Q

What are two main overviews of what the Stem and Leaf Plot can do?

A

Sort a large list of data, and graphically display the distribution of the data so that it can be described.

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5
Q

What are the three Usual things a Stem and Leaf plot can do?

A
  1. Determine the CENTER of the distribution
  2. Determine the RANGE OR SPREAD of the data
  3. Determine the SHAPE of the distribution
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6
Q

What are three Unusual things a Stem and Leaf plot can do?

A
  1. Determine any range of values not represented
  2. Determine if there is a concentration of data
  3. Determine if there are any outliers (extreme values)
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7
Q

How do you divide two digits numbers in a stem and leaf plot?

A

make one the stem and one the leaf

ex: 9|5 = 95. 9 would be the stem and 5 would be the leaf,

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8
Q

What is a Defining rule and why is it important?

A

A defining rule indicates how the stem and leaf plot should be interpreted. this allows someone to easily determine what each value represents.

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9
Q

Relating to quantitative variables what are the possible measurements divided into?

A

Class intervals. Each measurement should fall in one and exactly one interval.

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10
Q

What does a Standard Stem and Leaf plot consist of?

A

Divide each number in a set of data set into two parts: a “stem” and a “leaf” with two digit numbers. (can be used with 3, 4, or 5 digits, and w/ decimals.)

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11
Q

What is the digit in the Stem, and the digit in the Leaf?

A 
Stem= digit in the ten's place
Leaf= digit in the one's place
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12
Q

What’s the first thing to determine when creating your stem plot?

A

Your HIGHEST and LOWEST number.

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13
Q

How should you list the values vertically on the stem and leaf plot?

A

From smallest to largest.

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14
Q

When you list the data in the leafs they should also be from smallest to largest?

A

It is OPTIONAL at first so you can have little error, but once you have collected data you should list them from smallest to largest.

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15
Q

What is an example of a Defining rule?

A

9|5 = 95

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16
Q

What kind of digits can also be included in Standard leaf stem plots?

A

3,4 ,5, etc, digit numbers, and numbers with decimals.

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17
Q

What is considered a bad amount of Stems in a Standard stem and leaf plot?

A

less than 6 stems and more than 20.

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18
Q

What is considered a good amount of stems?

A

6-20 stems

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19
Q

What is the ideal amount of Stems you should shoot for?

A

10-15 stems.

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20
Q

How does an Extended Stem-and-Leaf Plot differ from a Standard?

A

You split the stems into two parts

the first leaf= digits from 0-4

the second leaf= digits from 5-9

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21
Q

What symbols are used in a Extended SAL plot to indicate # 0-4, and # 5-9?

A

0-4 = .

5-9 = *

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22
Q

Example of an Extended SAL Plot?

A
  1. = 0-4

3*= 5-9

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23
Q

What are the Adantages of Stem-and-Leaf Plots?

A
  • Display the distribution of the data
  • can be used to determine the center, spread, shape, and any unusual features
  • retain actual data
  • easy to construct
  • make sorting of the data easier
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24
Q

What are the Disadvantages of SAL Plots?

A
  • Not very effective for long data sets
  • choice of stems depends on the data type and data range
  • different choices for the stems can cause different looking distribution.
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25
Q

What are Back-to-Back Stem-and-Leaf plots used for?

A

To display two sets of data side-by-side, making it easier to compare the distributions.

26
Q

How do you create and use and Back-to-Back Stem-and-Leaf Plot?

A

Use a common column of stems with one distribution displayed on the left ((data) leafs), and one on the right.

27
Q

What are Histograms?

A

Graphical technique displaying quantitative data so that the distribution can be described.

28
Q

How are Histograms different from SAL Plots?

A

A histogram does not retain the original data.

29
Q

What will we only consider Histograms with?

A

Equal Class Widths.

30
Q

What is the first step when creating a Histogram?

A

Determine the # of Class intervals to use, always round up

31
Q

What are Class Intervals?

A

The intervals that will be on the x axis on the histogram.

32
Q

Example on how to get a Class interval: Subjects = 210.

A

To get the class interval you take the square root of the object, so the sq root of 210 is 14.5 so we round up to 15

33
Q

What is the 2nd step when creating a Histogram?

A

Determine the range

34
Q

How do we determine the range?

A

Subtracting the smallest observation from the largest. ex: 496-202= 294

35
Q

What is the 3rd step we take in creating a Histogram?

A

Divide the Range by the # of Class intervals to determine the CLASS WIDTH.

36
Q

Example of finding the class width. Range= 294. Intervals = 15

A

294/15 = 19.6 round to 20 so use a class width of 20 for each interval.

37
Q

What is the 4th step you take when creating a Histogram?

A

The lowest limit of the fist interval should be a multiple of the class width and should be able to contain the smallest observation in the data.

38
Q

Due to rounding in previous steps is it possible for the actual number of intervals to be one fewer or one more?

A

SI

39
Q

What is the 5th step when creating a Histogram?

A

Count the # of observations falling in each intervals. these are called frequencies/class frequencies.

40
Q

Relating to frequencies when you have two intervals such as 220-240, 240-260 where does 240 fall?

A

In 240-260, 220-240 239 is the highest that can go into 220-240.

41
Q

What is the 6th step when creating a Histogram?

A

Determine the Relative frequency for each class interval.

42
Q

How do you determine the Relative Frequency?

A

Dividing the Class frequency by the total number observations (subjects) and then multiplying by 100. Round to nearest tenth

43
Q

Example of determining Relative Frequency?

A

Interval 200-220 frequency = 4 and the # of observations = 210 then relative frequency= (4/210)*100= 1.9

44
Q

What is the 7th step when creating a Histogram?

A

Construct the Histogram.

45
Q

What goes on the X-axis on the Histogram?

A

Mark and label the Class Intervals.

46
Q

What Goes on the Y-axis of the Histogram?

A

The Class or Relative Frequencies.

47
Q

Relating to Shapes in Distribution, What is Symmetric Distribution?

A

A Distribution where the right and left sides of the distribution are mirror images of each other.

48
Q

Relating to Shapes in Distribution, What is Normal Distribution?

A

A type of symmetric distribution with a bell shaped curve in the data. Most commonly used type of distribution.

49
Q

Relating to Shapes in Distribution, What is Skewed Let Distribution?

A

General bell shape with long tail/outlier to the left

50
Q

Relating to Shapes in Distribution, What is Skewed Right Distribution?

A

General Bell Shape, Long tail/outlier to the right.

51
Q

Relating to Shapes in Distribution, What is Bimodal Distribution?

A

Distribution w/ 2 significant peaks.

52
Q

Relating to Shapes in Distribution, What is Trimodal Distribution?

A

A distribution w/ 3 significant peaks

53
Q

What is the center of the data?

A

The center just find around what it is

54
Q

What is the Spread of the data?

A

The range

55
Q

What are Unusual Features?

A

Not symmertric(normal) distributions. This includes; High concentrations of data, gaps in distribution, and Outliers.

56
Q

What is an Outlier?

A

An observation that stands out from other observations, often creates skewed data.

57
Q

For now, when describing the shape how should we do that?

A

Using the terms introduced

58
Q

For now how should we describe the Center of the data?

A

For now just a guess

59
Q

For now how should we describe the Spread of data?

A

For now use the range

60
Q

For now how should we describe Unusual features within the data?

A

Ouliers, Gaps, and High concentrations of data.

Stat 210 (5 decks)

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