Why data constructor is not in scope here

Question

I am trying to do Student T-test as provided here:

import Data.Vector as V
import Statistics.Test.StudentT
sampleA = V.fromList [1.0,2.0,3.0,4.0,1.0,2.0,3.0,4]
sampleB = V.fromList [2.0,4.0,5.0,5.0,3.0,4.0,5.0,6]
main = print $ StudentT sampleA sampleB SamplesDiffer

However, I am getting following error:

rnunttest.hs:8:16: error:
    Data constructor not in scope:
      StudentT :: Vector Double -> Vector Double -> PositionTest -> a0

Where is the problem and how can it be solved? Thanks for your help.

The data constructor is `StudenTTest`, not `StudentT`. – Willem Van Onsem Sep 12 '19 at 17:39 — Willem Van Onsem, Sep 12 '19 at 17:39
Ok. Yes, it works with `studentTTest`. – rnso Sep 12 '19 at 17:42 — rnso, Sep 12 '19 at 17:42

score 3 · Answer 1 · answered Sep 12 '19 at 17:42

3

I think you have to change the constructor to studentTTest

main = print $ studentTTest sampleA sampleB SamplesDiffer

answered Sep 12 '19 at 17:42

developer_hatch

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Willem Van Onsem · Accepted Answer · 2019-09-12T17:46:56.970

You made two mistakes here:

the function is studenTTest, not StudentT, that is the name of the type constructor; and
the constructor takes a PositionTest foollowed by two vectors.

import Data.Vector as V
import Statistics.Test.StudentT

sampleA = V.fromList [1.0,2.0,3.0,4.0,1.0,2.0,3.0,4]
sampleB = V.fromList [2.0,4.0,5.0,5.0,3.0,4.0,5.0,6]

main = print (studentTTest SamplesDiffer sampleA sampleB)

For the given sample data, this gives us:

Prelude V Statistics.Test.StudentT> main
Just (Test {testSignificance = mkPValue 1.351738152442984e-2, testStatistics = -2.8243130467507513, testDistribution = studentT 14.0})

is not that with lower case? – developer_hatch Sep 12 '19 at 17:43 — developer_hatch, Sep 12 '19 at 17:43

Why data constructor is not in scope here

2 Answers2