Question

The amount of time lost during the month due to accidents was determined before and after a new safety program was instituted at a manufactur ing firm. The sample sizes (number of months), m eans, and sta ndard deviations are sho wn below 8. Sample Size Sample Mean Sample Standard deviation 12.0 BEFORE AFTER 25 97.3 16 80.1 14.0 a. Find a 95% confidence interval for the (true) difference in mean lost time per month achieved by instituting the new safety program. b. Write the necessary assumptions needed for yo ur answers in (a) to be valid.

Answer 1

Salution 97.3 39. しーベーー0-95 to = 2.0 227 trac) differe nce- In mean lost timc per month achieved oy itu safety-pogrann-is givenas hit n2 2 x 14 x 11) (3600+3136) 2 16736) 2 9 2 S 172.7179

O 062 S n.2 ±(2-0 221) (7,7036 7.2 t 2.0227 x 4.2076 72t 8.5107 8.689 3 2S.7l07

e Necessa assumphan of for diferens 2 Parentapula tions om twhich the samples hav and independent 2 The peatievariances ar equal and untnoun ot cachether e4 is unknoun