Statistics week 1 - A way of organising, summarising and interpreting data Population of interest: - The 'things' we are interested in - Can be people, households, car manufacturers, trains - Population parameter: describes the entire population - Sample: - a subset of the population, - must be representative of the population - Variable - overarching label of the element/feature we want to measure. It must vary - e.g. gender, age Descriptive vs Inferential Stats - Descriptive: - organises raw information into manageable information - numerical and or graphical form - Inferential: - techniques that allow us to use sample stats to generalise to the population Types of Research - Descriptive - when we just want to found out 'something' (age of students studying this particular uni) - Correlational - exploring the relationship between two or more variable (relationship between height and weight) - Comparative Research - Compare two or more groups on the same measure Research Methods - Experimental Methods: - allows a cause-effect explanation - one variable (IV) is causing a change in the other (DV) - DV: dependent variable - IV: independent variable - Non experimental - does not allow a cause-effect explanation - both variables are observed/measured - observational
- Non experimental: - correlational - non-equivalent groups (comparing heights of males and females) o Iv not manipulated - Then and now Variables - Discrete o Fixed number of answer (how many children does a person have) Continuous - o Can have an infinite number of answers (height, weight, income) Measurement of Variables - Categorical o Nominal . Used to label the group (eg 1 = Male, 2 = Female) Order doesn't matter o Ordinal " Used to label AND order (eg 1st, 2nd, 3rd, fith in a race, Chapter 1, Chapter 2, Chapter 3 in Text) - Metric o Interval . Numbers are used to label and order AND the intervals between the numbers are equal. ff Does not mean absence of e.g. Temp of ff C. o Ratio " Numbers are used to label and order and the intervals between the numbers are equal AND zero means a complete absence of something (eg income or number of correct answers in a test). Can produce ratios (e.g. 5ff is exactly 1/2 of 1ffff but in interval, ff C is not a ratio of anything) Statistical Notation Population: - N represents the population size o Pop of Venezuela N = 32,67fi,532 o Pop of Trains on the XYZ line N = ??? - n = the sample size Raw Scores: - original, unchanged scores obtained from the data collection - Typically represented by X - If two then the other is Y Summing scores: - Sigma designates summation
o SigmaX means to add all the X values Hand Calculations Suppose there are scores of 2, 1, tt, 3 - Then: o SigmaX = 15 Order of Operations - Anything in brackets is done first - Squaring is done second - Multiplication or division is third, if more