Lec 1 Flashcards
Population of entities 👩👩👧👦👨👨👦👦👨👨👧👦
the largest collection of entities for
which we have an interest at a particular time
Population of values 🔢
largest collection of values of a
variable.
target population
target population is the population under study.
Define the sample ❓
specific subgroup of a population that
you will collect data from.
The size of a sample is always ❓
less than the total size
of the population (otherwise it’s not a sample
anymore).
Types of Statistics 📈
1- descriptive statistics 📊
2- inferential statistics 📈
Descriptive statistics include ❓
Descriptive statistics are used by
Collection
• Organization
• Summarization of data.
Descriptive statistics used by ❓
researchers to report on
populations and samples.
Define the variable and give 3 examples
variable is a characteristic that takes on different
values in different persons, places, or things.
• e.g.:
• Heights of adult males.
• Weights of preschool children.
• Ages of patients seen in a dental clinic
Type of variables
Two
1- Quantitative variables
The variable can be measured 🔢 in the usual sense of measurement as age 4️⃣9️⃣ years
Weight 4️⃣9️⃣ kg
Height 1️⃣6️⃣4️⃣ cm
2-Qualitative variables:- it is variable that (can not be measured ) in the usual sense but can be ‼️ categorized as
Disease 🦠
Healthy
A population which we are interested in studying is called:
A. Infinite population
B. Target population
C. Final population
D. Standard population
B
The WHO grades astrocytomas (a group of brain tumors) into 4
grades; labeled as grades I, II, III, and IV. The variable scale of
this grading system is:
A. Nominal
B. Ordinal
C. Numerical
D. Interval/ratio
B
Which of the following data represents an interval/ratio scale?
A. Ability to speak English
B. Smoking status recorded as: nonsmoker, current smoker,
ex-smoker
C. Gender
D. Height
D
Which of the following variables can be described as being
binary?
A. Age
B. Gender
C. Number of children
D. Blood group
B
Variable Scales
Nominal
Ordinal
Interval
Ratio
Type of Quantitative variables ⁉️
1- Discrete variable it is characterized by gaps or interruptions in the values that is can assume
The number of daily admissions
The number of decayed
Missing or filled teeth per child
2- continuous variable it does not possess the gaps or interruptions it can assume any value within a specific interval of values assumed by any variable
Weight
Height
Mid arm circumference
▪ Dichotomous (binary) variables
nominal variables which
have only two categories or levels. For example, “male or
female“, “yes or no”, etc..
Nominal scale
Use ⁉️
Is there specific order in it ❔
Another name of nominal scale ❓⁉️
مهم
Is it involve quantitative value or order ⁉️
uses names, numbers or other symbols. e.g. males &
females.
The variables are simply “named” or labeled, with no specific
order
Also called the categorical variable scale,
and doesn’t involve
a quantitative value or order.
👍🏻
Interval
Main characteristics
Each measurement is assigned to one of unlimited categories
that are equally spaced with no true zero point.
main characteristic of this scale is the equidistant
difference between objects.
Celsius/Fahrenheit temperature scales.
Ratio
Measurement begins at a true zero point and the scale has
equal intervals.
▪ Best examples of ratio scales are weight and height,
temperature in Kelvin.
Descriptive Statistical Work Includes
Collection
Organization of data
Summerization of data
Organization of data in descriptive statistics 📊 including ⁉️
Grouping
• Tables
• Frequency distribution (number of occurrences)
• Relative frequency distribution (proportion of occurrences)
• Graphs (histograms, pie charts, bar charts, polygons, etc…)
Summarization of data including
Measures of central tendency
• Measures of non-central tendency (centiles)
• Measures of variation
Grouping of Interval/Ratio Data
انواع ال grouping
1- Internationally agreed classifications
For example age is classified into: neonate (first 4 weeks), infant
(<1 year), toddler (second year of life), under 5 children, school age
children (5-9), teenagers (10-15), young adults (16-59), middle age
(60-79), elderly (80+)
Quantiles (percentiles, terciles and quartiles)
Very useful when no agreed method of classification is available. It
is unbiased and useful in detecting patterns or associations.
. Class intervals & Sturge rule
• Personal experience
Grouping of Data by Class Intervals
To group a set of observations
select a set of contiguous,
non overlapping intervals
- Each value in the set of observation can be placed in
one, and only one, of the interval. - No single observation should be missed.
Calculating the Number of Class Intervals
The number of class intervals should:
▪ Not be too few: because of the loss of important
information.
▪ Not be too many: because of the loss of the needed
summarization.
Sturge’s rule
We can follow Sturge’s Rule:
K= 1+3.322 log n
k= number of class intervals
n= number of observations in the set
من خلال هاي ال rule نحصل عدد الclass interval
Calculating the Width of Class Intervals
The width of the class intervals should be
should be the same
if possible
(an exception is often practically employed for the first and last
intervals)
W=R/ k
W= Width of the class interval
R= Range (largest value – smallest value)
K= Number of class intervals
Inferential Statistics
Analysis of data (reaching decisions
about a large body of data by
examining only a small number of
data).
