Question

decide whether each of the following statements makes sense (or is clearly true) or does not make sense (or is clearly false). explain your reasoning.

1. more than 1 million people sent texts in response to a survey question asked on tv, so this survey result is more valid than a survey of a random sample of 200 people.

1. the survey of religious beliefs suffered from selection bias because the questionnaires were handed out only at catholic churches.

1. my experiment proved that vitamin c reduces the severity of colds, because i controlled the experiment for every confounding variable.

1. everyone who jogs for exercise should try the new training regimen, because careful studies suggest it can increase your speed by up to 1%.

Explanation:

Question 5

A survey's validity depends on representativeness, not just sample size. The TV - text survey has a self - selected sample (only those who watch that TV show and choose to text respond), which is biased. A random sample of 200, though smaller, is more representative of the population, so the statement doesn't make sense.

Selection bias occurs when the sample is not representative. Handing out questionnaires only at Catholic churches means the sample consists mostly of Catholics, not a representative cross - section of people with different religious beliefs (or non - religious), so the survey has selection bias. The statement makes sense.

In an experiment, it's nearly impossible to control for every confounding variable. There could be unknown or unmeasured variables that affect the outcome. Also, "proved" is too strong a term for an experiment, as scientific conclusions are based on evidence and are tentative. So the statement does not make sense.

Answer:

Does not make sense. A large self - selected sample (TV text - in) is not necessarily more valid than a smaller random sample, as self - selection introduces bias.

Question 6