Types of Statistics

Definition

Statistics – a field of mathematics that provides us with the techniques that enable us to classify, summarize and draw valid inferences according to basic rules of evidence

Types of Statistics

A. Descriptive – is used to say something about a set of information that has been collected only.

the goal of descriptive statistics is to organize and to summarize data so that they are more readily understood

B. Inferential –

Inferential statistics is used to make predictions or comparisons about a larger group (a population) using information gathered about a small part of that population. Thus, inferential statistics involves generalizing beyond the data, something that descriptive statistics oes not do.

the goal of inferential statistics is to take into account the chance factors associated with sampling and subsequently draw valid conclusions

Other distinctions are sometimes made between data types.

• Discrete data are whole numbers, and are usually a count of objects. (For instance, one study might count how many pets different families own; it wouldn’t make sense to have half a goldfish, would it?)

• Measured data, in contrast to discrete data, are continuous, and thus may take on any real value. (For example, the amount of time a group of children spent watching TV would be measured data, since they could watch any number of hours, even though their watching habits will probably be some multiple of 30 minutes.)

• Numerical data are numbers.

• Categorical data have labels (i.e. words). (For example, a list of the products bought by different families at a grocery store would be categorical data, since it would go something like {milk, eggs, toilet paper, . . . }.)


III. Terminology

A. Population – the total group of observations about which one wants to draw a conclusion
1. A parameter is a measurable
characteristic of a population



2. Examples:
correlation proportion
mean s t andard deviation

B. Sample – any subset or subgroup of a population
1. Random samples occur when every element of the population has an equal chance of being selected or drawn
2. A statistic is a measurable characteristic of a sample
3. Examples:
r correlation p proportion
X mean S s t andard deviation
C. Variables – the characteristic we wish to
observe; properties by whereby members of a
group differ from one another
D. Ways to categorize variables
1. Quantitative vs. Qualitative
2. Discrete vs. Continuous
3. Dependent versus independent
E. Qualitative or nominal variables differ in kind rather
than amount (e.g., ethnicity, eye color).
F. Example:
Research question: What is the effect of preschool day
care on children?
- Dependent variable : IQ scores
- Independent variable: presence or absence of daycare
Research question: Do people with high IQs dream more?
- Dependent variable: REM (rapid eye movement)
- Independent variable: Level of IQ

Statistical data collection

What are data?

Data may be defined as a representation of facts or concepts or instructions in a formalized manner, suitable for communication, interpretation or processing by manual or electronic means. An element of data is an item, idea, concept or raw fact (Abdelhak et al., 1996).
In health care, these facts describe specific characteristics of individual patients. Whether we collect data on paper or in a computer, the data should be organized in such a way that we can understand and retrieve them when needed (Davis and LaCour, 2002).

Primary data are obtained from the original datasource. That is, documentation in the patient’smedical/health record collected by staff at either ahospital, clinic or aid post. Daily ward census reportscollected in hospitals are also primary data.

Secondary data are data sets derived from primarydata. Secondary data are individual or aggregatehealth care data found in reports that are summarizedfrom the source. At the hospital or health centre level,secondary data include the master patients’ index,
disease and procedure indexes, health care statistics anddisease registries. At primary care level, they alsoinclude such aspects as the patients’ name index andstatistics.