Page 205 - Applied Statistics Using SPSS, STATISTICA, MATLAB and R

186 5 Non-Parametric Tests of Hypotheses

p : Observed significance.
ksstat, lstat : Values of the Kolmogorov-Smirnov and Liliefors statistics,
respectively.
cv : Critical value for significant test.

Some of these parameters and return values can be omitted. For instance,
x
h = kstest(x) only performs the normality test of .
The arguments of the R function ks.test are as follows:

x: A numeric vector of data values.
y: Either a numeric vector of expected data values or a character string
naming a distribution function.
... Parameters of the distribution specified by y.

Commands 5.6. SPSS, STATISTICA, MATLAB and R commands used to obtain
cumulative distribution plots and normal probability plots.

Graphs; Interactive; Histogram; Cumulative
histogram
SPSS Analyze; Descriptive Statistics; Explore;
Plots; Normality plots with tests |
Graphs; P-P
Graphs; Histograms; Showing Type;
Cumulative
STATISTICA
Graphs; 2D Graphs; Probability-Probability
Plots
MATLAB cdfplot(x) ; normplot(x)

R plot.ecdf(x) ; qqnorm(x)

The cumulative distribution plot shown in Figure 5.2a was obtained with
MATLAB using the following sequence of commands:

» art = corkstoppers(1:50,3);
» cdfplot(art)
» hold on
» xaxis = 0:1:250;
» plot(xaxis,normcdf(xaxis,mean(art),std(art)))

Note the hold on command used to superimpose the standard normal
distribution over the previous empirical distribution of the data. This facility is
disabled with hold off . The normcdf command is used to obtain the normal
cumulative distribution in the interval specified by xaxis with the mean and
standard deviation also specified.