Data Overview: levels of measurement; frequency tables; histograms and boxplots; probability Flashcards
The advantages of Statistics:
- Numbers rich in information. Stats helps us to use this richness.
- Data are also treacherous. When in number format, statistics can tell us how much we can trust them.
- Stats makes the world a better place. E.g. infant care, Apgar score
What is a Measurement?
It express characteristic of an object as number.
What is a good measurement?
A good measurement is:
- reliable (stays the same over time)
- valid ( measurement is measuring what it is supposed to)
What is a Variable?
- It is a factor that can varies
- they can vary in their levels of measurements too
What is a Variable’s Level of Measurement?
- How much information they contain.
- What kind of mathematical operations are meaningful.
What are Ratio Scales and what do they do?
Most informative scale = gives the most amount of information
- it provides values that can apply mathematical reasoning and functions
- same/different;
- ranking;
- compute mean;
- compute ratio/percentage.
What are Nominal Scales and what do they do?
They give the least amount of information
- uses numbers for coding
- we cant apply any mathematical reasoning or functions to the codes
- same/different;
What are Equal Interval Scale and what do they do?
Most common scale in psychology
- difference between values is equal
- same/different;
- ranking;
- compute mean;
What are Ordinal scales and what do they do?
Scales values in an Order (1st, 2nd etc)
- same/different;
- ranking;
What are the characteristics of a Frequency Table?
- 1st column = range of values
- 2nd = how often the values appear
- the valid percentage column tells us what portion of the sample has a particular score
- the cumulative percentage column tells us what portion of the sample has that value or a lower value?
What are the characteristics of Histograms?
Histogram for same data:
- X-axis shows Value.
- Y-axis shows frequency.
What are the Shapes of Frequency Distribution?
- symmetric
- left-skewed (i.e., tail to the left)
- right-skewed (i.e., tail to the right)
- unimodal (mountain/ cliff = 1 peak)
- bimodal (rabbit ears = 2 peaks)
- rectangular
What are Kurtosis’ Pointiness of Distribution mean?
- Normal curve, kurtosis = 0
- Leptokurtic, kurtosis > 0 (sharper point)
- Platykurtic, kurtosis < 0 (very round point)
What are Boxplots for infatuation data?
They allow easy comparison across many groups.
- box = inter queartile or middle 50% values
- line in the box = median value
- whiskers = contain the 1.5 amount of the inter queartile range (larger and smallest scores)
- little circles = outliers
What is a probability?
Numerical expression of expectation the event that occurs.
