Basic Programming II

OutlineStandard Deviation Function (SD)Complex Guessing Game

Standard Deviation (SD)For the group of data, the standard deviation measures

the spread of the data.Given a set of data the standard deviation (SD) is calculated as

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where is the data, a is the average of the data,

is the number of data

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SDn

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Standard Deviation (SD)the procedure to compute the SD

1. Obtain the data,

2. Compute the average,

2. Compute the sum ,

3. Compute the SD,

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2

0( )

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12

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n

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Standard Deviation (SD): Accepting Data

Task1: Obtain the set of data Store 10 scores from the user in variable a[0],

a[1], ...,a[9]

#include <stdio.h>void main() { int a[10],n; for ( n=0 ; n<10 ; n++ ) { printf("Enter your data:"); scanf("%d", &a[n]); }}

0 1 1, ,..., na a a

Task 2 Compute the average,

Question1. What happens when we do not define csum=0 ?

Standard Deviation (SD)

#include <stdio.h>void main() { int a[10], n; float csum = 0, avg; for ( n=0 ; n<10 ; n++ ) { printf("Enter your data:"); scanf("%d", &a[n]); csum = csum + a[n]; } avg=csum/10.;}

0 1 1... na a aa

n

Task 3. Compute the sum of the square of the difference between the data and the average.

This can be done using pow function

pow((a[0]-avg),2)

Standard Deviation (SD)

12

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n

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Standard Deviation (SD)Task3. Continued

Store the sum in the variable, sq_sum

2)( xx

...#include <math.h>... float sq_sum=0;... for ( n=0 ; n<10 ; n++ ) { sq_sum = sq_sum + pow((a[n]-avg),2); }

Standard Deviation (SD)Task 4: Divide it by 10 and the take the square

root to complete the SD.

...#include <math.h> ... float sq_sum = 0, sd; ... for ( n=0 ; n<10 ; n++ ) { sq_sum = sq_sum + pow((a[n]-avg),2); } sd=sqrt(sq_sum/10);

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Standard Deviation (SD)SD

#include <stdio.h>#include <math.h>

void main() { float csum=0, avg, sq_sum=0, sd; int a[10], n; //get data and compute avg for ( n=0 ; n<10 ; n++ ) { printf("Enter your data:"); scanf("%d", &a[n]); csum = csum + a[n]; } avg=csum/10; //compute SD for ( n=0 ; n<10 ; n++ ) { sq_sum = sq_sum + pow((a[n]-avg),2); } sd=sqrt(sq_sum/10); printf(“SD = %.2f\n”, sd);}

Grade Assigning using SD

Once the SD has been computed, it can be used to assign the grade for each of the score.

Guessing Game (Again)Previously on

the Guessing game.

#include <stdio.h>#include <stdlib.h>#include <time.h>

void main() { int n, g, i = 1; srand(time(NULL)); n = rand() % 11; // generate a random number 0-10 do { printf("Guess a number[0,10]:"); scanf("%d", &g); i++; } while ((g!=n)&&(i<=5)); if (g == n) printf(“You got it.\n”); else printf("You failed. Please try again.\n");}

Guessing Game (Again)Improve the guessing game so that it tells

if the right answer is greater than the guess or less than the guess.

Guess a number[0,10]:2Greater than this.Guess a number[0,10]:6Less than this.Guess a number[0,10]:5You got it.

The random number (answer) is stored in variable n n

The guess is stored in variable g g

Guessing Game (Again)

Guessing Game (Again)Flowchart showing the relationship between

the guess and the number.{g==n You got it, g>n less than this, g < n

greater than this} g==n g>n

display ‘Less than this.’ display ‘Greater than this.’display ‘You got it.’

NN

Y Y

Guessing Game (Again)According to the flowchart, the translation

into code is if (g==n) { printf("You got it.\n");}else if (g>n) { printf("Less than this.\n");}else { printf("Greater than this.\n");}

#include <stdio.h>#include <stdlib.h>#include <time.h>

void main() { int n, g, i = 1; srand(time(NULL)); n = rand() % 11; // generate a random number 0-10 do { printf("Guess a number[0,10]:"); scanf("%d", &g); if (g==n) { printf("You got it.\n"); } else if (g>n) { printf("Less than this.\n"); } else { printf("Greater than this.\n"); } i++; } while ((g!=n)&&(i<=5)); if (g != n) printf("You failed. Please try again.\n");}

SummaryUsing flowchart can help us on planning

the program;When you cannot see the solution right

away, break the problem into smaller pieces and solve one at a time.