Hi $,$

i have checked this question in the tool before and i have been told that the right answer is A & B which is $$Two sample t$-$test based on shifts$$ & $4$ individuals charts, one per packer$$ however i have been marked as partially incorrect in the my academy study $.$ appreciate if an expert can check this for me please and let me know what is the correct answer?

Q$12$: The CS&F Web Fulfilment Team $($WFT$)$ have just introduced a Premium Package offering on the Uncle Jim's website. This consists of a gift wrapped box containing sweets, flowers and wine. The boxes need to be sturdy as well as carefully and neatly packed as the price to the customer is significant. As this is a new venture, the Management team are keen to understand their performance both now and as time progresses.

From their general pool of packers they have selected a team of $4$ experienced staff to handle these more complex orders. Each member has had special training. As a new venture, the team feel that the packing time is slower than it could be$,$ however this is OK at the moment as the emphasis has be on "getting it right" rather than speed. At the moment they are getting between $10-20$ Premium orders each day. They expect this to increase slowly to about $50.$ The packers have other duties but they premium packing task is their priority. At any time there could be between zero and the full team of $4$ working on Premium orders.

The WFT Management team is keen to understand the time taken to pack each order, so that they can demonstrate improvement, share best practice and generally remove waste. They want to know how each individual packer performs and also how the group performs and they want to see the changes over time.

Which TWO of the following would be the MOST useful tools to answer their questions.

Select one or more: need one more

A$)$ Two sample t$-$test based on shifts

B$)4$ individuals charts, one per packer

C$)$ A NP chart with a sample size of $4$

D$)$ An X$-$Bar and a S chart with each plot representing a working day

E$)$ An X$-$bar and a S chart with each plot representing a $2$ hour portion of the working day.