Tutor profile: Lina M.
Train A is headed south at 65 miles per hour, and train B heads east, 30 minutes after Train A departs at 50 miles per hour. After 45 minutes, train B reaches it's final destination. 15 minutes after that, train A reaches its final destination. What is the distance between trains.
Train A: Traveled for 30 minutes+45 minutes+15 minutes= 1:30 minutes 1.5 hours (65 m/h)(1.5hours)=97.5 miles Train B: Traveled for 45 minutes (50 m/h)(.75hours)=37.5 Now find the hypotenuse because one train went east and the other went south 97.5^2+37.5^2=c^2 (9506.25)+1406.25=c^2 10912.5=c^2 (10912.5)^.5=c 102.46=c
When should you use standard error over standard deviation?
Standard error measures precision of a mean or two means rather than the spread and variability of data. Standard deviation describes the entire set and does not even need a mean to rely on in order to portray information.
Given that the number of car accidents spikes up during Christmastime, can we assume that lights are distracting to drivers and cause them to crash? What other information might we need to determine whether or not lights cause accidents.
We would have to consider the weather conditions in which these accidents happen. The spike in car crashes could be due to dangerous road conditions and not lights. We must also consider the number of accidents that occur during the following months and whether or not the accidents actually go down. Perhaps we should also check the number of cars that are on the road during this time because it is likely that more people drive around during the holidays to visit family and friends. We cannot assume that holiday lights cause car accidents. This is a classic example of determining causation or correlation.
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