Lecture 3 Flashcards

1
Q

Lecture 3:

What are real limits when working with grouped frequency distribution?

A

Real limits help account for the rounding error between bins as the real limit is the middle value between 2 bins

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2
Q

Lecture 3:

What are the rules for real limits when working with grouped frequency distribution?

A

The lower real limit is 0.5… meaning add 5 on the end

The upper real limit uses 0.499 with one more decimal place than the data uses

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3
Q

Lecture 3:

What is a Percentile?

A

A point/position on a continuous scale of 100 such that a certain fraction of the population of raw scores lies at or below that point
-eg; 75th percentile = a score that is equal to or greater than 3/4 of the scores in the raw data set

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4
Q

Lecture 3:

Why are percentiles useful?

A

Useful because they use a standard score that is derived from raw data & has a known basis for comparison
- commonly used in clinical & educational settings

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5
Q

Lecture 3:

What are 2 things that standard scores allow us to do?

A

Allow us to;
1.) evaluate raw scores
2.) compare 2 sets of scores that have different units

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6
Q

Lecture 3:

When discussing common percentile divisions… what are quartiles & deciles?

A

Quartiles = quarters or groups of 25%

Deciles = 100 divided into blocks of 10 so divided into groups of 10%

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7
Q

Lecture 3:

What are the 3 key steps to calculating percentiles?

A

1.) Rank data in descending order
2.) count how many cases there are up to & including the target value
3.) divide # of cases by total sample (n) & multiply by 100

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8
Q

Lecture 3:

When calculating a percentile with a tie what do you do?

A

Since we define percentile as a fraction at or below a given score, we use the highest position when there is a tie as it is considered the “highest achievable value”

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9
Q

Lecture 3:

How do you determine a score if given the percentile?
- 4 steps?

A

1.) convert percentile to decimal
2.) multiply decimal by number of scores (n)
3.) round to the nearest interger
4.) Count that many scores up from the bottom

  • Example; if only the top 25% of class get an A…. Then you must find the score at the 75th percentile
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10
Q

Lecture 3:

When calculating a percentile using the equation… what does “X” represent?

A

The raw score

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11
Q

Lecture 3:

When calculating a percentile using the equation… what does “L” represent?

A

The lower real limit of the interval in which the raw score falls

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12
Q

Lecture 3:

When calculating a percentile using the equation… what does “i” represent?

A

The size of interval (the number of scores counted in a bin)

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13
Q

Lecture 3:

When calculating a percentile using the equation… what does “f” represent?

A

Frequency of the interval in which the raw score falls

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14
Q

Lecture 3:

When calculating a percentile using the equation… what does “C” represent?

A

The cumulative frequency of the interval immediately below the one in which X falls

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15
Q

Lecture 3:

When calculating a percentile using the equation… what does “N” represent?

A

The total number of cases

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