Types Of Statistical Studies - Khan Academy
The mayor of Statville has to decide how to allocate her education budget between the two high schools in town, "Stat Sticks" and "Datum High." To decide which school deserves a bigger portion of the budget, she went over the grade sheets of the students from both schools in the past 555 years, and analyzed the data. *What type of a statistical study did the mayor use? Sample study Experiment Observational study She found that the overall grade average of "Stat Sticks" students is 444 points higher than the overall grade average of the students of "Datum High." *What valid conclusions can be made from this result? Students from "Stat Sticks," in the last 555 years, had higher grades, on average, than students from "Datum High." The result suggests that "Stat Sticks" is a better high school than "Datum High." The result suggests that the students of "Stat Sticks" are cheating on the final exams. The result suggests that if a student went to "Stat Sticks" sometime in the past 555 years, their overall grade is 444 points higher than it would have been if they went to "Datum High" instead.
*1.) Observational Study *2.)Students from "Stat Sticks," in the last 555 years, had higher grades, on average, than students from "Datum High."
A zoologist had a hypothesis that there's a negative linear association between the average heart rate of a mammal species and its average life span. He gathered data about the average heart rate (in BPM - Beats Per Minute) and average life expectancy (in years) of hamsters, chipmunks, rabbits, cats, pigs, and horses. He obtained the almost linear scatter plot shown below. *What type of statistical study did the zoologist use? Sample study Experiment Observational study *Is the study appropriate for the statistical questions it's supposed to answer? Yes, because the results seem to corroborate the hypothesis. No, because the sample of species is too small and not necessarily representative. Yes, because the zoologist compared the heart rate of the mammal species to their life expectancy. No, because the study doesn't allow assessment of the effect of a mammal's average heart rate on its life expectancy.
*1.) Observational Study *2.) No, because the sample of species is too small and not necessarily representative.
The CEO of a major bank wanted to assess how many of the bank's customers are satisfied, so he decided to conduct a small survey. At the time of the survey, the bank had several millions of customers across 300300300 bank branches of varying sizes. For each of the 300300300 branches, he picked one of the branch's customers randomly and surveyed him. *What type of statistical study did the CEO use? Sample study Experiment Observational study *Is the study appropriate for the statistical questions it's supposed to answer? No, because the type of study chosen is inappropriate. No, because the randomization of the sampling was flawed. Yes, because the sample was big enough and obtained in an appropriate manner. No, because the study didn't have a control group and a treatment group.
*1.) Sample Study *2.) No, because the randomization of the sampling was flawed.
The chief of police in Statville wanted to estimate the amount of people above the age of 181818 who are using illegal substances in town. He obtained 200200200 random names of Statville residents from a computer database, and sent his officers to survey these people about substance abuse. Once the results came in, he calculated the margin of error and got an estimate of the percentage of residents who use illegal substances. *What type of statistical study did the chief of police use? Sample study Experiment Observational study *Is the study appropriate for the statistical questions it's supposed to answer? Yes, because the sample was big enough. No, because he didn't have a control group and a treatment group. No, because there's a great risk of obtaining biased answers. Yes, because his sample was chosen at random.
*1.) Sample Study *2.) No, because there's a great risk of obtaining biased answers.
A nutritionist had a hypothesis that eating a single banana an hour before a marathon (a 42\text{-km}42-km42, negative, k, m run) can improve performance and reduce running time. To test her hypothesis, she randomly assigned a group of 360360360 men about to participate in a marathon to two groups. One group was instructed to eat a single banana an hour before the race, and the other group was instructed to eat nothing during the few hours before the race. After the race was done, she compared the average running times of the two groups. *What type of statistical study did the nutritionist use? Sample study Experiment Observational study The nutritionist found that the average running time of the group who ate a banana was 555 minutes shorter than the running time of the group who hadn't. Based on some re-randomization simulations, she concluded that the result is significant and not due to the randomization of the groups. *What valid conclusions can be made from this result? The result suggests that any runner will likely run a faster marathon if they eat a banana an hour before the race as opposed to eating nothing. The result suggests that a male runner will likely run a faster marathon if he eats a banana an hour before the race as opposed to eating anything else. The result suggests that a male runner will likely run a faster marathon if he eats a banana an hour before the race as opposed to eating nothing. The result suggests there's a correlation between eating a single banana before a marathon and reduction in running time for male runners.
*1.) Experiment *2.) The result suggests that a male runner will likely run a faster marathon if he eats a banana an hour before the race as opposed to eating nothing.
