Introduction and descriptive statistics Flashcards
what are the 2 main types of data in statistics?
- qualitative/categorical
- quantitative/numerical
what are the types of categorical/qualitative data?
what are the types of quantitative/ numerical data?
in qualitative/categorical data, if we have 2 categories, what is it called?
binary
in qualitative/categorical data, if we have more categories but they are just named, what is it called?
nominal
in qualitative/categorical data, if we have categories that have an order, what is it called?
ordinal
does qualitative data have anything to do with qualitative research?
no - it is 2 different concepts
give an example of categorical data/ qualitative
- Colour of a person’s hair (black, gray, red, blonde, brown, …)
- Gender of a child (male, female)
- County of residence of a British citizen (Southeast, Southwest, London, Midlands, Yorkshire, Northeast, Northwest,…)
what is categorical data with only 2 levels called?
binary
what is another word for binary data
Dichotomous
give examples of binary data
- Dead/alive
- Treatment/placebo
- Disease/no disease
- Exposed/Unexposed
- Heads/Tails
- Caries (yes/no)
- Male/female
categorical data
describe nominal data
named categories
order doesnt matter
give examples of nominal data
- The blood type of a patient (O, A, B, AB)
- Marital status
- Occupation
categorical data:
describe ordinal data
categorical data
order matters
categorical data:
give an example of ordinal data
- Stages of cancer: I, II, III, or IV
- Birth order: 1st, 2nd, 3rd, etc.
- Ratings on a scale from 1-5
- Socio-economic status
- Education level
- Age in categories (10-20, 20-30, etc.)
what is Quantitative data?
Numerical variables; may be arithmetically manipulated.
give an example of quantitative data
- Number of patients in a dental hospital per day (counts: 0, 1, 2, 3)
- Survival time of a patient diagnosed with oral cancer (nearest day: 0, 1, 2, …, 10000)
- Number of teeth (counts: 0,1,2,3,…)
- Weight of a child: kg
whats a good way of seeing whether data is quantitative/numerical or not?
add up the values and if it is numerical then it is probably numerical
quantitative data - what are discrete numbers?
a limited set of distinct values, such as whole numbers.
quantitative data - list some examples
- Number of new patients registered in your dental practice in a year (counts)
- Years of school completed
- The number of children in the family (cannot have a half a child!)
- DMFT/DMFS score (total number of teeth or surfaces that are decayed (D), missing (M), or filled (F) in an individual)
Quantitative data - define continuous data
Can take on any number within a defined range.
Quantitative data - list some examples
- Time
- Age
- Blood pressure
- Speed of a car
- Width of a central incisor
What types of data is the following (binary, nominal, ordinal, numerical discrete or numerical continuous)?
number of teeth
discrete
What types of data is the following (binary, nominal, ordinal, numerical discrete or numerical continuous)?
age
continuous
What types of data is the following (binary, nominal, ordinal, numerical discrete or numerical continuous)?
(age last birthday (years))
discrete
What types of data is the following (binary, nominal, ordinal, numerical discrete or numerical continuous)?
Has patient visited their dentist in the last year?
binary
What types of data is the following (binary, nominal, ordinal, numerical discrete or numerical continuous)?
Socio-economic status
ordinal
What types of data is the following (binary, nominal, ordinal, numerical discrete or numerical continuous)?
Pocket depth
continuous
What types of data is the following (binary, nominal, ordinal, numerical discrete or numerical continuous)?
Hardness of filling material
This depend on how you measure hardness? In numerical values or in category?
What types of data is the following (binary, nominal, ordinal, numerical discrete or numerical continuous)?
Colour of filling material
nominal
What types of data is the following (binary, nominal, ordinal, numerical discrete or numerical continuous)?
Type of radiograph
nominal
What types of data is the following (binary, nominal, ordinal, numerical discrete or numerical continuous)?
Calcium : phosphorus ratio in teeth
continuous
frequency plots - what kind of plots do we use for categorical data?
bar chart
why would we use histograms or box plot for continuous data?
To show the distribution (shape, center, range, variation) of continuous data/variables.
Distribution Shape and Box-and-Whisker Plot show the same thing
visualising data/ summary measures
when describing data numerically, what 2 things would we focus on?
central tendancy
variation
how do we calculate the mean
what is the mean affected by?
The mean is affected by extreme values (outliers)
what is the median calculation?
If there are an odd number of observations, find the middle value
If there are an even number of observations, find the middle two values and average them
is the median affected by extreme values/ outliers?
no
list the measures of dispersion
Quartiles
what is the first quartile?
Q1, is the value for which 25% of the observations are smaller and 75% are larger
Quartiles
what is the second quartile?
Q2 is the same as the median (50% are smaller, 50% are larger)
Quartiles
what is the third quartile?
Only 25% of the observations are greater than the third quartile Q3
how is interquartile range calculated?
what may interuatile range be represented by?
box plot
define sample variance
Average (roughly) of squared deviations of values from the mean
why do we square deviations?
d
a
what is the role of the shape of a distribution?
- Describes how data are distributed
- Measures of shape
* Symmetric or skewed
if the distribution is left-skewed, what does that indicate about the relationship between the mean and median?
if the distribution is symmetric, what does that indicate about the relationship between the mean and median?
if the distribution is right-skewed, what does that indicate about the relationship between the mean and median?
a
c
c
c
d
a
a
