Unit 1 - Descriptive Statistics Flashcards

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1
Q

What are the measures of central tendency?

A

Mean, Median, Mode.

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2
Q

How is the mean calculated?

A

Add all numbers together, divide by number of participants.

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3
Q

How is the median calculated?

A

Middle number, put numbers into order ranging from lowest to highest, choose middle.

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4
Q

How is the mode calculated?

A

Most occurring.

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5
Q

What is a strength of the mean?

A

Accurate average, and takes into account all the scores.

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6
Q

What is a weakness of the mean?

A

Outlier scores can skew the mean to not reflect most participants.

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7
Q

What is a strength of the median?

A

Not affected by outlier scores, so results will not be skewed.

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8
Q

What is a weakness of the median?

A

Does not take into account all scores.

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9
Q

What is a strength of the mode?

A

Can be used for non-numerical data.

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10
Q

What is a weakness of the mode?

A

Impossible to calculate if all data is different, or the may be more than one mode.

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11
Q

What are the measures of dispersion?

A

Range, Variance, Standard Deviation.

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12
Q

How is the range calculated?

A

Largest score minus smallest score.

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13
Q

How is the variance calculated?

A

For each condition, calculate the mean. Within each, subtract each participant’s score from the mean for that condition (‘d’ difference). Then square each ‘d’ score (d^2). Then add all d2 scores together to get Ed2, then subtract by n-1.

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14
Q

How is standard deviation calculated?

A

Square root of variance.

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15
Q

What is a strength of range?

A

Quick and easy to calculate.

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16
Q

What is a weakness of range?

A

Data can be skewed by outliers, only takes into account top and bottom values.

17
Q

What is a strength of variance?

A

Takes into account all values, less likely to be affected by outliers.

18
Q

What is a weakness of variance?

A

Only takes into account the squared values, not original units the data was first in.

19
Q

What is a strength of SD?

A

Takes into account all data, expressed in same unit as original.

20
Q

What is a weakness of SD?

A

Time consuming and more difficult to calculate than range.

21
Q

How to convert fractions to a percentage?

A

Divide top of fraction by bottom, multiply by 100.

22
Q

How to convert a percentage to a fraction?

A

Write percentage over 100, simply fraction, if not a whole number, multiply top and bottom by 10 for every number after the decimal point.

23
Q

How to find actual number of a percentage of an amount?

A

Divide amount by 100 and multiply by percentage.

24
Q

How to find actual number represented by fraction of an amount?

A

Divide amount by the denominator (bottom) and multiply by numerator (top)

25
Q

What is a frequency table?

A

A way of presenting data - tally chart. WHEN = observation

HOW = tally of behaviour

26
Q

What is a line graph and when and how is it used?

A

Shows behaviour changes over time. Includes X and Y axis, labelled.

27
Q

What, when and how do you use a pie chart?

A

Works well with nominal data, enables researcher to present percentages, includes labels and titles. WHEN = observation
HOW = percentage converted into decimal (divide by 100), 360 multiplied by decimal to calculate the degree.

28
Q

What, when and how do you use a bar chart?

A

Conveys information about frequencies through height of the bar.
WHEN = experiments
HOW = (1 mark) data plotted accurately, (1 mark) detailed title, (1 mark) both axis labelled (y axis - mean rating) (x axis - what you’re measuring), (1 mark) mentioning mean rating, y axis must start at 0, bars must be spread apart.

29
Q

What, when and how do you use a histogram?

A
Conveys information about frequencies through area of the bar, used with continuous data, emphasised by the category width. 0< x < 2 (time), frequency (number of people), time (class width), frequency / class width (frequency density). WHEN = experiments
HOW = title, axis labelled, bars touching, area represents frequency, unusual class width.
30
Q

When and how are scatter graphs used?

A
WHEN = correlations
HOW = pattern and strength. ‘uphill’ = positive correlation, ‘downhill’ = negative correlation, ‘spread apart’ = no correlation.
31
Q

How are ratios calculated?

A

= divide the amount of by total number of parts and then multiply by the original ratio.