Stats Final- Unit 3

does donating blood lower cholesterol levels? 50 volunteers have a cholesterol test, then donate blood, and then have another cholesterol test. which aspect of this experiment design is present?

NOT a placebo, no control group, no randomization, no blinding

each property owner has 5 digit ID number. use a random number to choose 40 numbers

SRS

in an experiment the primary purpose of blinding is to reduce..

bias

in an experiment the primary purpose of blinding is to reduce?

bias

placebos are a tool for?

blinding

which of the following is not required in an experimental design?

blocking

if we wish to compare the avg PSAT scores of boys and girls taking A Stats at this high school, which would be the best way to gather these data?

census

we wish to compare the average ages of the math and science teachers at your school. which is the best way to collect data?

census

randomly select a housing class (say, apartments) and survey all the ppl who live in that property classification

cluster

have each firefighter survey 10 of his neighbors

convenience

a researcher wants to compare the effect of a new type of shampoo on hair condition. he believes that men and women may react differently to the shampoo. he also believes that the shampoo will react differently on hair that is dyed. the subjects are split into four groups: men/women who do/dont dye their hair. subjects in each group are randomly assigned to the new shampoo and the old. this experiement

has one factor ( shampoo type), blocked by gender and whether it is dyed or not

a researcher wants to compare the performance of three types of pain relievers in volunteers suffering from arthritis. bc ppl of diff ages may suffer arthritis of varying degrees of serenity, the subject are split into two groups:under 60 and over 60. subjects in each group are randomly assigned to take one of the medications. 20 mins later they rate their heels of pain. this experiment..

has one factor (medication) blocked by age

which is true about bias?

its results from a sampling method likely to produce samples that do not represent the population

among a dozen eggs, three are rotten. a cookie recipe calls for two eggs; they'll be selected randomly from that dozen. which plan could be used to stimulate the number of rotten eggs that might be dozen?

let 0,1,2 rep the rotten eggs, and 3-11 the good eggs. generate two random numbers 0-11, ignoring repeats

a bball player has a 70% free throw percentage. which plan could be used to stimulate the number of free throws she will make in her next five free throws?

let 0,1,2 represent missing a shot and 3-9 represent making a shot. generate five random numbers 0-9 and count how many numbers are in 3-9

a factory has 20 assembly lines producing a popular toy. to inspect a representative sample of 100 toys, quality control staff randomly selected 5 toys from each line's output. was this a SRS?

no, bc not all combinations of 100 toys ould have been chosen

suppose the state decides to randomly test high school wrestlers for steroid use. there are 16 teams in the league, and each team has 20 wrestlers. state investigators plan to test 32 of these athletes by randomly choosing two wrestlers from each team. is this a SRS?

no, bc not all possible groups 32 wrestlers could have been the sample

to check the effect of cold temps on the battery ability to start a car, researchers purchased a battery from sears and one for NAPA. they disabled a car so it would not start, put the car in a warm garage, and installed the sears battery. they tried to start the car repeatedly, keeping track of the toal time that elapsed before the battery could no longer turn the engine over. then they moved the car outdoors where the temp was below zero. after the car has chilled there for several hours, the researchers installed the NAPA battery and repeated the test. is this a good experimental design?

no, bc temp is confounded by brand

can watching a movie temporarily raise your pulse rate? researchers have 50 volunteers check their pulse rates. then they watch an action film, after which they check their pulse rates once more. which aspect o experimentation is present in this research?

none of these: control group, blinding, randomization, placebo

more dogs are being diagnosed w thyroid props than have been diagnosed in the past. researcher identified 50 puppies without the prob and kept records of their diets for several years to see if an developed thyroid probs. this is a

prospectie study

does regular exercise decrease the risk of cancer? a researcher finds 200 women over 50 who exercise regularly, pairs each with a woman who has similarly medical history but does not exercise, then follows the subjects for 10 years to see which group develops more cancer. this is a

prospective study

which is important in designing a good experiment?

randomization in assigning subjects to treatments control of potentially confounding variables replication of the experiment on a sufficient number of subjects

20 dogs and 20 cats were subjects in an experiment to test the effectiveness of a new flea control chemical. 10 of the dogs were randomly assigned to na experimental group that wore a collar containing the chemical, while the others wore a similar collar without the chemical. the same was done with the cats. after 30 days the vets were asked to inspect the animals for fleas and evidence of flea bites. this experiment?

randomized block, blocked by species

a company sponsoring a new internet search engine wants to collect date one the east of using it. what is the best way to collect the date?

sample survey

which true about sampling?

sampling error is the result of random variations and is always present

the city has 5 property classifications: single fam homes,apartments, condominiums, temporary housing (hotel and campgrounds) and retail. randomly select ten residents from each category

stratified

at the start of each week, survey every tenth person who arrives at the city park

systematic

double-blinding in experiments is important so that

the evaluators and participants do not know which treatment group the participants are in

hoping to get info that would allow them to negotiate new rates with their advertisers, Natural health magazine phoned a random sample of 600 subscribers. 64% of those polled said they use nutritional supplements. which is true?

the pop of interest is the ppl who read the magazine. this sampling design should provide the co. w a reasonably accurate estimate of the percentage of all subscribers who use supplements

the jan 2005 gallup youth survey telephoned a random sample of 1028 us teens and asked these teens to name their favorite movie from 2004. naoploean dynamite had the highest percent w 8% teens ranking it as fav. whats true?

the pop of interest is us teens 8% is statistic and not actual percent of all us teens who would rank this movie as fav this sampling design should provide a reasonable accurate estimate of the actual percentage of all us teens who would rank this movie as their fav

the owner of a car dealership planned to develop strategies to increase sales. he hoped to learn the reasons why many ppl who visit his car lot don't eventually buy a car. for one month he asked his sales staff to keep a list of names and addresses of everyone who came in to test a car. at the end of the month he sent surveys to the ppl who didn't buy the car, asking them why. about 1/3 of them returned the survey, with 44% of those indicating they found a lower price elsewhere. which is true?

the pop. of interest is all potential car buyers this survey design suffered from non-response bias.

a chemistry professor who teaches a large lecture class surveys his students who attend his class about how he can make the class ore interesting, hoping he can get more students to attend. this survey method suffers from

undercoverage

in an experiment the primary purpose of blocking is to reduce

variation

suppose your local school district decides to randomly test high school students for attention deficit disorder. there are three high schools in the district, each with grades 9-12. the school board pools all of the students together and randomly samples 250 students. is this a srs?

yes, bc they could have chosen any 250 students from throughout the district