Difference between revisions of "Manuals/calci/CHITEST"

From ZCubes Wiki
Jump to navigation Jump to search
 
(40 intermediate revisions by 5 users not shown)
Line 1: Line 1:
<div style="font-size:30px">'''CHITEST(ar,er)'''</div><br/>
+
<div style="font-size:30px">'''CHITEST (ActualRange,ExpectedRange)'''</div><br/>
*<math>ar</math> is the array of observed values
+
*<math>ActualRange</math> is the array of observed values.
*<math>er</math> is the array of expected values
+
*<math>ExpectedRange</math> is the array of expected values.
 +
**CHITEST(), returns the test for independence.
  
 
==Description==
 
==Description==
*This function gives the  the value from the chi-squared distribution. i.e it calculates <math>\chi^2</math> statistic and degrees of freedom, then calls CHIDIST.  
+
* It is a test for independence.
 +
* This function gives the value from the chi-squared distribution and the appropriate degrees of freedom i.e it calculates <math>\chi^2</math> statistic and degrees of freedom, then calls CHIDIST.  
 
The conditions of <math>\chi^2</math> test is  
 
The conditions of <math>\chi^2</math> test is  
 
  The table should be 2x2 or more than 2x2
 
  The table should be 2x2 or more than 2x2
Line 11: Line 13:
 
  Each cell has an expected frequency of at least five.
 
  Each cell has an expected frequency of at least five.
 
*The <math>\chi^2</math> test first calculates a <math>\chi^2</math> statistic using the formula:
 
*The <math>\chi^2</math> test first calculates a <math>\chi^2</math> statistic using the formula:
<math>\chi^2 = \sum_{i=1}^{columns} \sum_{j=1}^{rows} \frac{(observed ij-expected ij)^{2}}{grand total}</math>
+
<math>\chi^2 = \sum_{i=1}^{columns} \sum_{j=1}^{rows} \frac{(observed _{ij}-expected _{ij})^{2}}{grand total}</math>
*<math>observed ij</math> is the array of the observed values in a given set of values
+
*<math>observed _{ij}</math> is the array of the observed values in a given set of values
*<math>expected ij = \frac{(column i total)*(row j total)}{grand total} </math>
+
*<math>expected _{ij} = \frac{(column _i total)*(row _j total)}{grand total} </math>
 
*observed and expected must have the same number of rows and columns and there must be atleast 2 values in each.
 
*observed and expected must have the same number of rows and columns and there must be atleast 2 values in each.
 
*A low result of <math>\chi^2</math> is an indicator of independence.
 
*A low result of <math>\chi^2</math> is an indicator of independence.
 
*From the formula of <math>\chi^2</math> we will get <math>\chi^2</math> is always positive or 0.
 
*From the formula of <math>\chi^2</math> we will get <math>\chi^2</math> is always positive or 0.
*0 only if <math>observed ij = expected ij</math> for each <math>i</math> and <math>j</math>.  
+
*0 only if <math>observed _{ij} = expected _{ij}</math> for each <math>i</math> and <math>j</math>.  
 
*CHITEST uses the <math>\chi^2</math> distribution with the number of Degrees of Freedom df.
 
*CHITEST uses the <math>\chi^2</math> distribution with the number of Degrees of Freedom df.
where <math>df=(r-1)(c-1),r>1</math> and <math>c>1</math>.
+
*where <math>df=(r-1)(c-1),r>1</math> and <math>c>1</math>.
If <math>r=1</math> and <math>c>1</math>, then <math>df = c-1</math> or if <math>r>1</math> and <math>c=1</math>, then <math>df = r-1</math>.
+
*If <math>r=1</math> and <math>c>1</math>, then <math>df = c-1</math> or if <math>r>1</math> and <math>c=1</math>, then <math>df = r-1</math>.
 
  If <math>r = c = 1</math> then this function will give the error result
 
  If <math>r = c = 1</math> then this function will give the error result
 +
*The obtained result is entered in the Chi square distribution table with the obtained degrees of freedom.
 +
*This returns the test for independence (probability).
 +
 +
==ZOS==
 +
*The syntax is to calculate CHITEST in ZOS is <math>CHITEST (ActualRange,ExpectedRange)</math>.
 +
**where <math>ActualRange</math>is the array of observed values.
 +
**<math>ExpectedRange</math>is the array of expected values.
 +
*For e.g;CHITEST([60,72,86,45],[57.08,75.10,87.1,42.45])
 +
{{#ev:youtube|gh-b_MUMo9c|280|center|Chi-Squared Test}}
  
 
==Examples==
 
==Examples==
A student investigated the chance of getting viral fever for a period of a school that took vitamin tablets every day.
+
A student investigated the chance of getting viral fever in a school for a period that took vitamin tablets every day. The total number of students 880. In that 639 students didn't get viral fever and 241 students got fever .But the expected ratio is 1:3<br/>
A student investigated whether taking vitamin tablets every day for a school term affected peoples chances of getting a Viral fever during the period. The total number of students 880. In that 639 students didn't get viral fever and 241 students got fever .But the expected ratio is 1:3.
+
'''Answer'''
'''Answer''':
+
*If the ratio is 1:3 and the total number of observed individuals is 880, then the expected numerical values should be: 660 will not get fever and 220 students will get fever.   
If the ratio is 1:3 and the total number of observed individuals is 880, then the expected numerical values should be 660 didn't get and 220 students will get that fever.   
 
  
                      Didn't get fever        Get fever
+
{| class="wikitable" style="width:50%" align="center"
observed          639                          241
+
|-  
values               
 
 
 
Expected
 
values              660                            220
 
{| id="TABLE3" class="SpreadSheet blue"
 
|- class="even"
 
!
 
! No Fever
 
! Get Fever
 
|- class="odd"
 
! Observed Values
 
| 639
 
| 241
 
|- class="even"
 
! Expected Values
 
| 660
 
| 220
 
|}
 
{| class="wikitable" style="width:100%";
 
|-
 
 
!  
 
!  
 
! No Fever
 
! No Fever
Line 62: Line 52:
 
| 660
 
| 660
 
| 220
 
| 220
 +
|-
 +
! <math>\frac{(oi-ei)^2}{ei}</math>
 +
| 0.668
 +
| 2
 
|}
 
|}
  
 +
*The <math>\chi^2</math> value is 2.668
 +
*Now <math>df=(r-1)(c-1) = (2-1)(2-1) = 1 </math>
 +
*From the Chi Squared Distribution probability table with <math>df</math> is 1, the <math>\chi^2</math> value of 2.668 is  0.10.<br/>
 +
CHITEST(or,er) = 0.10
  
(oi-ei)^2/ei        0.668                        2
+
==Related Videos==
The x^2 value is 2.668
 
Now df=(r-1)(c-1)=(2-1)(2-1)=1
 
From the chisquared distribution probability table with df is 1 for the X^2 value 2.668 is  0.10.
 
i.e CHITEST(or,er)=0.10"
 
  
 
+
{{#ev:youtube|UPawNLQOv-8|280|center|Chi Square Test}}
Let’s see an example
 
B C
 
45 38
 
10 23
 
12 26
 
40.5 49.36
 
19.56 16.44
 
17.05 17.41
 
CHITEST (a, b)
 
i.e. =CHITEST (B2; C4, B5:C7) is 0.003
 
  
 
==See Also==
 
==See Also==
Line 89: Line 73:
 
==References==
 
==References==
 
[http://en.wikipedia.org/wiki/Chi-squared_distribution  CHI-SQUARE Distribution]
 
[http://en.wikipedia.org/wiki/Chi-squared_distribution  CHI-SQUARE Distribution]
 +
 +
 +
 +
*[[Z_API_Functions | List of Main Z Functions]]
 +
 +
*[[ Z3 |  Z3 home ]]

Latest revision as of 09:57, 2 June 2020

CHITEST (ActualRange,ExpectedRange)


  • is the array of observed values.
  • is the array of expected values.
    • CHITEST(), returns the test for independence.

Description

  • It is a test for independence.
  • This function gives the value from the chi-squared distribution and the appropriate degrees of freedom i.e it calculates  statistic and degrees of freedom, then calls CHIDIST.

The conditions of test is

The table should be 2x2 or more than 2x2
Each observations should not be dependent
All expected values should be 10 or greater. 
Each cell has an expected frequency of at least five.
  • The test first calculates a statistic using the formula:

  • is the array of the observed values in a given set of values
  • observed and expected must have the same number of rows and columns and there must be atleast 2 values in each.
  • A low result of is an indicator of independence.
  • From the formula of we will get is always positive or 0.
  • 0 only if for each and .
  • CHITEST uses the distribution with the number of Degrees of Freedom df.
  • where and .
  • If and , then or if and , then .
If  then this function will give the error result
  • The obtained result is entered in the Chi square distribution table with the obtained degrees of freedom.
  • This returns the test for independence (probability).

ZOS

  • The syntax is to calculate CHITEST in ZOS is .
    • where is the array of observed values.
    • is the array of expected values.
  • For e.g;CHITEST([60,72,86,45],[57.08,75.10,87.1,42.45])
Chi-Squared Test

Examples

A student investigated the chance of getting viral fever in a school for a period that took vitamin tablets every day. The total number of students 880. In that 639 students didn't get viral fever and 241 students got fever .But the expected ratio is 1:3
Answer

  • If the ratio is 1:3 and the total number of observed individuals is 880, then the expected numerical values should be: 660 will not get fever and 220 students will get fever.
No Fever Get Fever
Observed Values 639 241
Expected Values 660 220
0.668 2
  • The value is 2.668
  • Now
  • From the Chi Squared Distribution probability table with is 1, the value of 2.668 is 0.10.

CHITEST(or,er) = 0.10

Related Videos

Chi Square Test

See Also

References

CHI-SQUARE Distribution