What are the measures of central tendency and dispersion
Mean, median, mode, range and standard deviation
Discuss and evaluate mean
Add up all numbers and divide by N ratio and interval data only
Most sensitive because uses exact distance, distorted by extreme values, but not appropriate for ordinal data or discrete values
Discuss and evaluate the median
Are you unselect midpoint the ratio, interval and ordinal data
Useful for extreme values, but not as sensitive as mean
Discuss and evaluate the mode
Most common value or group. Maybe bimodal. Can be used with all levels of measurement
Useful for nominal data, but not good when there are many modal groups
Discuss and evaluate the range
Subtract lowest from highest and add the correction of one
Easy to calculate, but affected by extreme numbers and doesn’t reflect the data distribution
Discuss and evaluate standard deviation
Average distance between each number and the main
Takes exact values into account may be affected by extreme values
How do you display quantitive data
Tables and graphs must have a title and clear labels
Tables may contain measures of central tendency and dispersion
Bar chart, histogram, line graph, scattergram
Explain a bar chart
Height of bar represents frequency, date on X axis may not be continuous
Explain the histogram
Represents frequency of continuous data, true zero and bobs next to each other
Explain a line graph
Frequency represented by a line rather than bars
Explain a scattergram
Shows correlation between covariables
What are the types of data distributions
Normal distribution, positive skew, negative skew
Discuss a normal distribution
Symmetrical bell shaped curve; mean, median and mode at midpoint; about 68% of people are one standard deviation above and below the midpoint, 95% within two standard deviation from midpoint
Discuss a positive skew
Tail to right, occurs eg: test too hard
Discuss a negative skew
Tail to left, because e.g. when test to easy
What are the types of data
Quantitive
Qualitative
Primary
Secondary
Discuss and evaluate quantitive data
Numerical, easy to analyse but may not represent reality
Discuss and evaluate quantitative data
Can’t be directly counted, detailed and possibly unexpected information, but more difficult to draw conclusions
Discuss and evaluate primary data
Collected by the researcher for current study, involves design a study to collect data. Suits the needs of the study, but time-consuming and expensive
Discuss and evaluate secondary data
Using data collected for previous study. Saves time and money but may not fit exact needs of study
When do you use the sign test
With paired or related data
How do you do the sign test
Represent each pair of data with plus or minus, calculated value of S= less frequent sign
Look up critical value of S, need to know N and whether one-tailed or two-tailed test
Conclusion is if the calculation value is less than or equal to critical value the difference is significant
Probability level of 5% is commonly used
