ISIA P&S L1 C2 S2

Intro Stats: Islamic Approach -- Part 2: Probability and Statistics -

Lecture 1: Random Samples, Concept 2: Populations Slide 2: Example: WDI Data on Countries

This is a data set from WDI -- World Development Indicators. Here the Population is the set of all countries. Characteristics listed here are the Life Expectancy and the GNP per capita in 2005. The full data set is attached in EXCEL spreadsheet. This is called a CROSS-SECTION data set. It is a picture of different objects at a SINGLE POINT IN TIME (usually). The KEY to a CROSS SECTION is that the ORDER of the data DOES NOT MATTER. We can re-arrange the countries in any sequence, the data will provide the same information. This is not true for time series data

Note the large number of dots near the bottom on the x-axis. These dots are for countries which have LOW GNP per capita, but a WIDE range variation in life expectancies, going from 38 to 74. Similarly note the big HORIZONTAL cluster toward the right hand side. These are all countries with HIGH life expectancy, above 70. Note the wide range of INCOME variation in this cluster. One can achieve very high life expectancies with a fairly low level of GNP per capita. Even though USA has the highest GNP per capita, it does not have highest life expectancy. Recent statistics show a HUGE differential in the USA, with poor people having 15 years LOWER life expectancy than the richest people.

There are TWO IMPORTANT SKILLS that students should learn. One is to LOOK at data sets and try to understand what they are telling us. Many important lessons are contained in this small data set. Note that the countries with GNP below 5000 have an ENORMOUS variation in Life Expectancies. This means that low income NEED NOT cause poor health and low life expectancy. Even at low income levels, some countries do very well, while other countries do very badly with respect to life expectancy. Some other factors (different from GNP per capita) must be IMPORTANT in determining life expectancy. What factors are these? We should search for them. It would be very important. Anoth