When measuring disease frequency, proportions and rates are very helpful when comparing groups, because they relate the number of people with disease to the size of the population in which they occur. Prevalence and incidence are the two fundamental measures of disease frequency.

The Doppler effect is used to measure the velocity detected objects where a radar beam is fired at a moving target. For example, the police use radar to detect a speeding vehicle. Radio waves are fired using a radar gun at the moving vehicle.

The frequency is characteristics of the source and hence it does not change with distance.

The frequency of sound doesn’t decrease with distance, but it does derease with increasing distance, meaing it does go through the doppler shift, same as light. This is why the sound of a car driving by at high speeds drops in frequency as the car passes you.

The Mean from a Frequency Table

1. Add the numbers: 6 + 11 + 7 = 24.
2. Divide by how many numbers (there are 3 numbers): 24 ÷ 3 = 8.

Data can also be presented in graphical form. Histograms and bar charts are both visual displays of frequencies using columns plotted on a graph. The Y-axis (vertical axis) generally represents the frequency count, while the X-axis (horizontal axis) generally represents the variable being measured.

To find the relative frequencies, divide each frequency by the total number of students in the sample–in this case, 20. Relative frequencies can be written as fractions, percents, or decimals. Relative frequency = frequency of the classtotal.

A frequency table is a method of organizing raw data in a compact form by displaying a series of scores in ascending or descending order, together with their frequencies—the number of times each score occurs in the respective data set.

A frequency table is a table that keeps a tally of how often certain events occur. A tally is simply a running total. Frequency tables are most useful when keeping track of how many times something happens. In other lessons we’ll discuss additional tools we can use for other statistical purposes.

The frequency table records the number of observations falling in each interval. Frequency tables are useful for analyzing categorical data and for screening data for data entry errors. Note that we will refer to two types of categorical variables: Categorical and Grouping or Break.