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Jawab:

Nilai fi xi fi.xi
30 – 34 2 32 64

35 – 39 6 37 222

40 – 44 10 42 420

45 – 49 16 47 752
50 – 54 6 52 312

JUMLAH 40 - 1.770

Mencari rata-rata ( ̅ )
∑ . ̅
̅ = =1
∑
=1
1.770
̅ =
40

̅ = 44,25

Jadi, ragam/variansnya adalah
2
∑ . ( ̅ − ̅ )

2 =1
=
∑
=1

2
2
2. (32 − 44,25) + 6. (37 − 44,25) +
10. (42 − 44,25) + 16. (47 − 44,25) +
2
2
6. (52 − 44,25)
2
2
= 40

2
2
2. (−12,25) + 6. (−7,25) +
2
2
10. (−2,25) + 16. (2,75) +
2
6. (7,75)
2
=
40