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Byju's Answer
Standard XII
Mathematics
Standard Deviation about Mean for Continuous Frequency Distributions
If a coin is ...
Question
If a coin is tossed three times and
X
=
number of heads, then find
E
(
X
)
and
V
(
X
)
.
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Solution
S
=
{
H
H
H
,
H
H
T
,
H
T
T
,
H
T
H
,
T
T
T
,
T
T
H
,
T
H
T
,
T
H
H
}
coin is tossed three time
2
3
=
8
,
x
=
0
,
1
,
2
,
3
P
(
x
=
0
)
=
P
(
T
T
T
)
=
1
8
P
(
x
=
1
)
=
P
(
x
=
1
)
=
3
8
P
(
x
=
2
)
=
3
8
P
(
x
=
3
)
=
1
8
E
(
x
)
=
Σ
x
i
f
i
=
0
×
1
8
+
1
×
3
8
+
2
×
3
8
+
3
×
1
8
=
3
+
6
+
3
8
∴
E
(
x
)
=
12
8
=
3
2
V
(
x
)
=
Σ
x
i
2
f
i
=
0
2
×
1
8
+
1
2
×
3
8
2
2
×
3
8
+
3
2
×
1
8
=
3
8
+
12
8
+
9
8
=
24
8
V
(
x
)
=
3
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