Answer
$Nonparametric\:statistics\:should\:be\:used\:when\:$
$the\:population\:is\:not\:normally\:distributed\:or\:when\:$
$testing\:hypotheses\:that\:do\:not\:involve\:specific\:$
$population\:parameters\:- e.g.,\:mean,\:standard\:$
$deviation.$
Work Step by Step
$The\:parametric\:tests\:are\:used\:when\:the\:population\:is\:normal.\:Similarly,\:the\:non-parametric\:test\:is\:used\:when\:the\:population\:is\:not\:normal.\:In\:other\:words,\:the\:non-parametric\:statistics\:is\:used\:when\:the\:population\:from\:which\:the\:samples\:are\:selected\:is\:not\:normally\:distributed.\:The\:non-parametric\:statistics\:can\:also\:be\:used\:to\:test\:hypotheses\:that\:do\:not\:involve\:specific\:population\:parameters,\:such\:as\:μ,\:σ\:οr\:ρ.$
