3.1 Types of Data Flashcards

1
Q

What are the two types of descriptive statistics?

A
  1. Categorical - Discrete - qualitative
  2. Continuous - quantitiative
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2
Q

What are the two types of categorical data?

A
  1. Nominal
  2. Ordinal
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3
Q

What is Nominal data?

A
  • Discrete categories
  • Cannot be ordered or ranked

e.g. blood type, colour, dead or alive

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4
Q

What is Ordinal data?

A
  • Discrete categories that can be ranked
  • The ‘gap’ between each category is not numerically defined

e.g. GCS, mild/moderate/severe

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5
Q

How is categorical data presented?

A
  • Percentages
  • Frequencies

e.g. bar charts

The data is summarised in a way that someone with the summary could extract the data back out

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6
Q

What are the two types of continuous data?

A
  • Interval
  • Ratio
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7
Q

What is Interval data?

A
  • Not necessarily discrete
  • No ‘none’ category
  • Gap between values is equal at all points on the scale

e.g. temperature or time of day

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8
Q

What is Ratio data?

A
  • ‘None’ is available
  • Gap is equal along the scale

e.g. pain score, days since an MI

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9
Q

How is continuous data (interval and ratio) presented?

A

Histograms which can either be normal or skewed

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10
Q

What are the measures of central tendancy for normal distributions?

A
  • Mean
  • Standard deviation
  • Variance
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11
Q

What is the mean of a normal distribution?

A

The middle

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12
Q

What is the Standard Deviation?

A

How much the data varies around the mean

  • SD = √Σ(x-mean)2
    ____________
    n-1
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13
Q

What is the Variance?

A

The standard devation squared

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14
Q

What are the two types of skewed continuous data?

A

Negative - hump to the right
Positive - hump to the left

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15
Q

How is a negative skew normalised?

A

with exponential transformation e.g. square or e^x

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16
Q

How can you tell a negatively skewed data set?

A

mean < median

17
Q

How is a positively skewed data set normalised?

A

Normalise with log transformation

18
Q

How can you tell a positively skewed data set?

A

mean > median

19
Q

What are the measures of central tendancy for skewed data sets?

A
  • Median
  • Interquartile range (25th and 75th percentile)
  • 5 numer range: min - 25th - median (50th) - 75th - max
20
Q

How are the measures or central tenancy presented?

A

Box plot

21
Q

What is another name for a normal distribution?

A

Gaussian

22
Q

What are the standard deviations?

A

68% of data is within 1 S.D of the mean
95% of data is within 1.96 S.D of the mean
99.7% of data is within 3 S.D of the mean

23
Q

What is the reference range of a normal distribution?

A

mean ± (1.96 x S.D)