Although more than 81% of total restaurant sales are paid by card (either credit or debit), some customers still prefer to pay with either cash or by using personal checks.

	DF	SS	MS	F	P
Groups		299.11			0.0010
Error	203	4258.94	20.98

The tables above shows an incomplete ANOVA Table with a (simulated randomization) p-value that researchers from Ohio State University constructed to determine if, based on a sample of 206 individuals, the mean amount that customers tip differs between the three payment methods.[1]

Use the descriptive statistics below to find the margin of error for a 95% pairwise comparison of customers who pay using cards to those who pay using cash.

Group	N	Mean	SD
Card	167	0.169	0.041
Cash	33	0.145	0.035