Who know about statistics

How to do a Z-test with Megastat

Z-tests are used to discover if there is a significant difference in the means of data sets 30 or greater. No not have zero’s or words (nominal data, women, men, etc.) in your data sets.

See slides 108 &109 in Power Point Presentation in the Instructor Announcements under Yellow Brick Road.

See the Z-test sample paper and Megastats in the Student Materials.

First understand that you must have two different sets of the same type of data. You can compare apples and oranges as long as you measure their weight or total sales but you cannot compare weight and sales. They will certainly be different. Example below: ATM transactions on two different machines over a 30-day period.

ATM 1	ATM 2
100	115
130	120
125	131
88	114
96	88
112	96
150	132
147	143
111	121
142	135
96	95
155	130
137	145
144	152
98	100
101	136
120	127
150	152
151	140
100	99
115	143
128	132
120	152
116	113
122	125
139	140
130	148
100	92
145	135
150	146

Open Excel, log in both data sets. Go to Add Ins, Megastat, Hypothesis Tests, Compare Two Independent Groups, left mouse click highlight Group 1 then Group 2, check the Z-test in the box, OK.

This will appear in the output tab at the bottom of the spreadsheet:

Hypothesis Test: Independent Groups (z-test)

ATM 1	ATM 2
123.93	126.57	mean
20.50	19.45	std. dev.
30	30

	-2.633	difference (ATM 1 - ATM 2)
	5.159	standard error of difference
		hypothesized difference

	-0.51	z
	.6098	p-value (two-tailed)

Retain the null hypothesis, the p-value of p=.60 is larger than the alpha level of significance of .05. There is no significant difference between the two ATM machines as measured by transactions.

Copy and paste to your paper.

Use p-value in the Student Materials and slides 66-69 in Power Point Presentation in the Instructor Announcements under Yellow Brick Road to help you reject or retain the null hypothesis to determine if the data sets are significantly different or the same.

I hope this helps,

Dr. Loro