sampling

Question 1

what are bad sampling plans?

Answer 1

• convenience sampling
• voluntary response sampling
• they systematically favour certain outcomes and often produce inaccurate results (biased)

Question 2

what is convenience sampling?

Answer 2

• selecting individuals that are easiest to reach
• interviewer makes the choice

Question 3

study this example on convenience sampling

Answer 3

Mall interviews: Manufacturers and advertising
agencies often use interviews at shopping malls to
gather information about the habits of consumers
and the effectiveness of ads (a fast and cheap
approach!)
Are the people contacted at shopping malls are
representative of the entire population?
* No! Mall samples are biased: they systematically
over-represent some parts of the population:
prosperous people, teenagers, and retired people.
➢ Moreover, the interviewers tend to select neat, well
dressed and safe-looking individuals.

Question 4

what is voluntary response sampling?

Answer 4

• allowing individuals to choose to be in the sample
• only people who are interested will participate

Question 5

study this example on voluntary response sampling?

Answer 5

Ann Landers (1918–2002), a famous American advice columnist,
once asked the readers of her advice column in 1975:
➢ If you had it to do over again, would you have children?
She received nearly 10,000 responses, almost 70% saying “NO!”
Can it be true that 70% of parents regret having
children? Not at all, the results are strongly biased
✓ The percentage of parents who would not have children again
is much higher in her sample than in the population of all
parents.
✓ Other examples: call-in opinion polls (usually in response to
a question or topic presented on a TV or radio show, or even
online platforms)

Question 6

who makes the choice in a convenience sample?

Answer 6

the interviewer

Question 7

who makes the choice in a voluntary response sample?

Answer 7

the people choose whether to respond

Question 8

which one produces bias?

Answer 8

BOTH of them

Question 9

what are good sampling techniques?

Answer 9

a sample chosen by CHANCE

Question 10

what does a sample chosen by chance allow

Answer 10

allows neither favortism by the sampler nor self-selection by respondentst. it removes BIAS
ex: picking names out of a hat

Question 11

what does SRS stand for?

Answer 11

simple random sample