| Class interval | $0-10$ | $10-20$ | $20-30$ | $30-40$ | $40-50$ | $50-60$ | $60-70$ | $70-80$ | $80-90$ | $90-100$ |
| Frequency | $3$ | $2$ | $4$ | $6$ | $5$ | $5$ | $5$ | $2$ | $8$ | $5$ |
| Class marks | Mid value $\left(x_i\right)$ | $d _{ i }= x _{ i }- a = x _{ i }=45$ | $f _{ i }$ | $f _{ i } d _{ i }$ | $d_i$ | $f _{ i } d_i$ |
| $0-10$ | $5$ | $-40$ | $3$ | $-120$ | $1600$ | $4800$ |
| $10-20$ | $15$ | $-30$ | $2$ | $-60$ | $900$ | $1800$ |
| $20-30$ | $25$ | $-20$ | $4$ | $-80$ | $400$ | $1600$ |
| $30-40$ | $35$ | $-10$ | $6$ | $-60$ | $100$ | $800$ |
| $40-50$ | $45$ | $0$ | $5$ | $0$ | $0$ | $0$ |
| $50-60$ | $55$ | $10$ | $5$ | $50$ | $100$ | $500$ |
| $60-70$ | $65$ | $20$ | $5$ | $100$ | $400$ | $2000$ |
| $70-80$ | $75$ | $30$ | $2$ | $60$ | $900$ | $1800$ |
| $80-90$ | $85$ | $40$ | $8$ | $320$ | $1600$ | $12800$ |
| $90-100$ | $95$ | $50$ | $5$ | $250$ | $2500$ | $12500$ |
| $\sum f _{ i }=45$ | $\sum f _{ i } d _{ i }=460$ | $\sum f _{ i } d_i=38400$ |
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