Question

Calculating Mean, Median, and Mode (Individual Data)

Individual data – represents individual values in a set.

Mean – is the average value of the values in a set. It is calculated by dividing the sum of the individual values in a set by the number of values in that set.

Median – better represents a measure of central than the mean in a set of data that are skewed one direction or another. To calculate the median value of individual data, do the following:

1. Rank-order the values ascending or descending order;

2. Identify the mid-point of the sequence;

• If there is an odd number of values, identify the middle number

• If there is an even number of values, identify the mid-point between the two numbers in the middle of the sequence. To identify the mid-point or the median case of a sequence of values: [Total number of the values in the sequence + 1 / 2]

3.Take the value of the mid-point or the median case as the median value in the set.

Mode – is the number of times each value occurs in the set, and selecting that value that occurs most often.

Given: The following represent the age in years of persons involved in a small outbreak.

1, 7, 3, 2, 3, 39, 4, 8, 3, 24.

Calculate the mean, median, and mode.

Calculating Mean, Median, and Mode (Grouped Data)

Grouped data – can be obtained for a “simple frequency distribution” based on single units of specific

measurement units being used. The measurement units could be specified in hours, days, weeks, etc. The cases are tabulated according to the specific number of hours, days, weeks, etc that lapsed between the time the case was exposed to the agent and the time at which the case became ill.

Given: The frequency distribution of the incubation periods, in a single day, of 41 cases among persons in a common source outbreak is presented. (see Table)

Calculate –

1. The mean incubation period.

2. The median incubation period.

3. The modal incubation period

SOLVE THESE PROBLEMS (A - D) AND SHOW WORK !

Computation of Rates

A. During 1977, in a city of 212,000 population, a total of 1,900 persons died during the year, four (4) of the deaths were from disease “a”.

1. What was the crude death rate per 1,000 population?

2. What was the cause-specific death rate per 100,000?

B. During the same period, a total of 412 cases of measles were reported in the same city. What was the incidence rate per 100,000 population in the city during the specified period?

C. It was also known that 19 of the cases were males under 10 years of age. At that time, the male population under 10 years of age was 19,080.

What was the age-specific incidence rate during that year in the city?

What was the sex-specific incidence rate during that year in the city?

D. An outbreak involved 26 cases of disease “x”, 7 were female, 19 were males. The total number of persons of each sex in the affected group was unknown. (See Table below)

Sex   # of Cases # of Persons (in group)

Male 19 87

Female 7 9

Total 26 96

What was the attack rate among members of each sex, and among the entire group?

What was the was the proportitional distribution of cases by sex?

Answer 1