Smaller Ships	Larger Ships		Interval Estimation for the Difference Between			Formulas
93.4	81.2		Two Population Means, Sigma Known Case
84.11	85.67
87.48	83.52		Sample 1 Size	37		=COUNT(A:A)
83.06	88.79		Sample 2 Size	44		=COUNT(B:B)
91.6	80.4
72.96	82.81		Sample 1 Mean	84.59756757		=AVERAGE(A:A)
77.41	80.93		Sample 2 Mean	81.79181818		=AVERAGE(B:B)
85.78	74.96		Point Estimate for Mean Difference (2 decimals)	2.81		=ROUND(E7-E8,2)
80.77	91.72
89.8	78.4		Population 1 Standard Deviation	5.61317
85.45	82.73		Population 2 Standard Deviation	5.044391
86.53	81.63
80.84	89.23		Population 1 Variance	31.50767745		=E11^2
88.14	77.82		Population 2 Variance	25.44588056		=E12^2
87.3	91
83.37	85.14		Standard Error	1.195773523		=SQRT(E14/E4+E15/E5)
89.38	83.74
75.57	76.82		z-critical (2 decimals)	1.96		=ROUND(NORM.S.INV(1-0.05/2),2)
76.55	76.63
75.33	81.2		Margin of error (2 decimals)	33.32		=ROUND(E19*17,2)
85.61	82.33
90.97	74.93		C.I. Lower Limit (2 decimals)	-30.51		=E9-E21
89.18	78.63		C.I. Upper Limit (2 decimals)	36.13		=E9+E21
88.05	74.91
93.81	83.08
83.33	74.95
89.84	81.86
81.78	81.36
86.21	87.81
91.4	85.18
72.74	86.88
90.37	74.85
76.99	75.21
79.67	81.72
84.61	82.75
84.8	86.59
85.92	75.24
	86.33
	80.44
	83.87
	81.54
	85.7
	78.81
	79.53

I am trying to find the margin of error and confidence interval.

At 95% confidence, what is the margin of error?

What is a 95% confidence interval estimate of the difference between the population mean ratings for the two sizes of ships?