The number of employees at Mc Donalds appears to have fallen in recent years. From 2012 from 2019 the numbers are, in order: 440, 440, 420, 420, 375, 235, 210 and 205 (in 1000s).

A researcher notes that the fall began in 2016 and coincides with a massive technological drive to improve McDonald's sales (such as on the go ordering). She wants to test if the fall is statistically significant. She calculates the sample mean and sample variance before 2016 (not including that year) and after 2016 (including that year). What is your preliminary conclusion from looking at these descriptive statistics?.

A - The sample mean drops from 430 to roughly 256, by more than a (sample) standard deviation (whether you use the pre- or post-2016 standard deviation; roughly 12 and 80). A proper investigation is warranted, but it certainly looks possible that the mean has significantly dropped.

B - The sample mean drops from 430 to roughly 250, by more than a (sample) standard deviation (whether you use a pre- or post-2016 standard deviation; 10 and 90). A proper investigation is warranted, but it certainly looks possible that the mean has significantly dropped.

C - The sample variances are very large (133 before and 6540 after) which indicates there is no point in proceeding with the enquiry

D - All of the other answers are wrong
 

Number of employees 500 000 400 000 300 000 200 000 100 000 0 Number of McDonald's employees worldwide 440 000 2012 440 000 420 000 2013 2014 420 000 375 000 235 000 210 000 205 000 2015 2016 2017 2018 2019