The means are compared with the corresponding certified values using a student t
test at 95 percent confidence interval to determine the acceptability of the test
results. The critical t test value for n¼15 at 95 percent CI is t0.95¼1.761, for n¼9 at 95
percent CI is t0.95¼1.859 and for n¼6 at 95 percent CI is t0.95¼2.015. The actual value
of t was calculated using: tcalc ¼ jx−μj=ð
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
s2=n þ δ2
q
Þ, where n refers to the number of
determinations, x is the analysis mean, μ is the certified mean, s is the standard
deviation, and δ is the certified standard deviation. When the tcalc for all tests is lower
than tcrit, the tests conducted for the vegetables are accepted (Mullins, 2003).