Population and Samples

Population VS Sample ◦ Population is a group of all things that share a set of characteristics. ◦ Population parameter – the value that would be obtained if the entire population were actually studied.

◦ Sample is a subset of population that is intended to represent the population. ◦ Sample statistic – the value obtained from the sample. It is used to estimate the population parameter value.

Pharmaceutical Biostatistics: Descriptive Statistics

Population VS Sample cont. ◦ A set of data is a sample from our population. The sample is a subset of the population. ◦ Statistical inference – the process that we used to draw conclusions from a data. ◦ Inference involves using statistics we calculate from the sample to make and informed guess about population. ◦ When we do statistical inference we are interested in drawing conclusions from a set of data (sample) so that we can estimate population parameters.

Pharmaceutical Biostatistics: Descriptive Statistics

We want to know about these‌ We have these to work with

RANDOM SELECTION

sample

population

INFERENCE

​ â &#x; đ?‘‹ (sample mean)

Îź (population mean)

Sample statistic

Population parameter Pharmaceutical Biostatistics: Descriptive Statistics

Population vs Sample cont.

Pharmaceutical Biostatistics: Descriptive Statistics

Population vs Sample cont. #

Example (task)

Population

Sample

1

Characterisation of the weights of tablets in a particular batch

All tablets that constitute the batch

100 tablets selected for weighing

2

Evaluation of the IQ of school All school children in Selangor in year 1 children in Selangor in year 1

100 children in year 1 attending selected schools in Selangor

3

Evaluation of the worldwide incidence of head injury in professional boxers

Examination of the medical records of all professional boxers in the UK

All professional boxers worldwide

Pharmaceutical Biostatistics: Descriptive Statistics