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Question: I have a sample size of 58 for a process improvement on reducing spending. My improvement lasted ...

I have a sample size of 58 for a process improvement on reducing spending. My improvement lasted for 9 weeks, 5 weeks I collected 40 receipts of expenses before and after my process improvement I collected 18 receipts. I need to calculate the Standard deviation for the process before the correction. X=40 and than the correction after x=18 . I need to find the confidence interval as well. ( I NEED THE X=40 first process standard deviation)(I need the X=18 for the second standard deviation) I also need to find the the confidence interval. Please help me!

(1st group of 40 expenses) 59.73 71.58 29.35 18.81 2.66 2.66 21.73 33.65 57.48 24.00 63.15 8.99 33.10 9.10 4.67 23.30 38.40 5.53 18.95 83.05 10.32 4.67 3.10 29.83 63.36 68.16 7.99 29.31 68.10 27.69 287.68 34.16 8.89 61.44 $7.30 $6.60 $2.61 $24.66 117.42 11.71 = 1484.89

(2nd group of 18 expenses) $24.00 $4.24 $10.58 $2.99 $32.21 $7.84 $2.99 $4.48 $52.32 $2.49 $6.30 $4.07 $3.32 $57.11 $4.19 $19.01 $7.99 $31.69 $7.30 $6.60 $2.61 $24.66 = $318.99