Statistics Flashcards
What is Descriptive statistics?
Summarises a given data set (graphically or numerically). Aim to provide a shorthand description of large amounts of data.
What is Inferential statistics?
Used to draw conclusions about a population from studying a sample.
define a Population
A large group e.g All students from University.
define a Sample
A small number taken from a large group.
What are variables?
Variables are characteristics of individuals, objects or events that can take on different values or amount. e.g blood pressure, weight, age, sex.
What are observations?
Outcomes (value) of the measurement or registration. e.g 120/60 mmHg, 70kg, 35 years, male etc.
Types of Variables are:
Qualitative (categorical) and Quantitative (numerical)
3 Different types of qualitative variables are:
BINARY- Two distinct categories. (e.g male and female).
NOMINAL - names or categories. (single, married).
ORDINAL - Data is ordered in terms of degree (e.g social class 1-5).
2 different types of quantitative variables:
CONTINOUS - (Measurable) it is a measurement on a continuous scale. e.g blood pressure 143.4 mmHg.
DISCRETE- (COUNTABLE) Ir can only take a limited number of discrete values. For example number of children in a family 2 or 3.
How do you summarise qualitative (categorical) data?
- Count the number of observations. These counts are called frequencies.
How do you present qualitative (categorical) data?
- Using numbers (table): Frequencies (e.g male and female)
- Using graphs = Pie chart & Bar chart.
What are the length of bars in a bar diagram proportional to?
Frequency
What is a section in a pie chart proportional to?
Percentage
What are 2 ways to summarise numerical data?
Using Numbers - measures of central tendency and variation.
Using graphs/ tables - histograms and frequency polygon.
What is Ordered Array?
It is a list of the observations in order of the increasing magnitude from the lowest value to highest.
Also makes it easier for more calculation and further organisation to be done.
What does the decision maker or scientist get a feel for when looking at ordered array?
The magnitude of the data.
Other than ordered array, how else can the data be classified?
Frequency distribution. (Look for patterns in the data set). However can make a long table of data and make it complicated.
After ordered array and frequency distribution, Whats a further grouping method of data?
Class Intervals.
What are classes?
They are groups the data is organised into.
What are class limits?
They are the smallest and largest observations in each class. Therefore, each class has two limits a lower and upper.
Classifying the data with too few intervals results in….
Excessive loss of information.
Classifying the data with too many intervals results in…
Defeating the purpose of summarisation.
How can frequency distribution be explained as?
How frequent certain things happen within a set of data.
How can frequency distribution be presented graphically?
Histogram
Differences between a Bar Chart and Histogram
Bar chart =
- Categorical Data
- Bars in a bar chart are not contiguous
Histogram=
- Numerical Data
- Bars of a histogram are contiguous.
When testing for normality what result indicates normality?
a non significant result (sig value of greater than 0.05) indicates normality.
What are tests for normality?
Kolmogorov-smirnov (K-S) and shapiro-wilk (S-W).
When are scewness values significant?
1.96 or less than -1.96 are significant
