BOTA 302 BIOSTATISTICS PRACRICAL 1
SAMPLING AND PROBABILITY DISTRIBUTIONS
Simple random sample: Every member and set of members has an equal chance of being
included in the sample. Technology, random number generators, or some other sort of chance
process is needed to get a simple random sample.
Activity 1
White and black balls are put in container. Shake the container and without looking inside you
pick one ball and record the colour. Repeat the process until you pick 10 balls
Activity 2
Using the information obtained in 1 above
a) Calculate probability of getting a white and black ball
b) Determine binomial probability distribution for all possible outcomes for the ten balls.
Stratified random sample: The population is first split into groups. The overall sample consists
of some members from every group. The members from each group are chosen randomly.
Activity 3
Sort the different types of seeds provided into different groups. The pick a sample of 4 seeds
from each type and combine in one container.
(a) What is the total sample size?
(b) What are the advantages of this sampling procedure over simple random sample?
Multistage sampling design
Multistage sampling design involves selection successively of similar groups within the
population in stages. Each stage may employ an SRS, a stratified sample or another type of
sample.
Activity 4
We shall assume that the area around whether station in Dept. represents a county. We need to
determine infestation of maize by weevils in the county. Divide area into 4 regions and in each
region into 4 Zones and zones into 4 farming areas and finally farming area into 10 farms. Maize
grains will sampled from stores of the farms
(a) What is the total sample size?
(b) Sketch this sampling design
SAMPLING AND PROBABILITY DISTRIBUTIONS
Simple random sample: Every member and set of members has an equal chance of being
included in the sample. Technology, random number generators, or some other sort of chance
process is needed to get a simple random sample.
Activity 1
White and black balls are put in container. Shake the container and without looking inside you
pick one ball and record the colour. Repeat the process until you pick 10 balls
Activity 2
Using the information obtained in 1 above
a) Calculate probability of getting a white and black ball
b) Determine binomial probability distribution for all possible outcomes for the ten balls.
Stratified random sample: The population is first split into groups. The overall sample consists
of some members from every group. The members from each group are chosen randomly.
Activity 3
Sort the different types of seeds provided into different groups. The pick a sample of 4 seeds
from each type and combine in one container.
(a) What is the total sample size?
(b) What are the advantages of this sampling procedure over simple random sample?
Multistage sampling design
Multistage sampling design involves selection successively of similar groups within the
population in stages. Each stage may employ an SRS, a stratified sample or another type of
sample.
Activity 4
We shall assume that the area around whether station in Dept. represents a county. We need to
determine infestation of maize by weevils in the county. Divide area into 4 regions and in each
region into 4 Zones and zones into 4 farming areas and finally farming area into 10 farms. Maize
grains will sampled from stores of the farms
(a) What is the total sample size?
(b) Sketch this sampling design
