Correct Answer - D
Since
1+3p
4
,
1-p
4
,
1+2p
4
and
1-4p
4
are probabilites when X takes values -1,0,1
and 2 respectively. Therefore, each is greater tahn or equal to 0 and less than or equal to 1.
i.e., 0≤
1+3p
4
≤1,0≤
1-p
4
≤1,0≤
1+2p
4
≤1and0≤
1-4p
4
≤1⇒-
1
3
≤p≤
1
4
0
≤
1
+
3
p
4
≤
1
,
0
≤
1
−
p
4
≤
1
,
0
≤
1
+
2
p
4
≤
1
and
0
≤
1
−
4
p
4
≤
1
⇒
−
1
3
≤
p
≤
1
4
Let
ˉ
X
be the mean of X. Then,
ˉ
X
=-1×
1+3p
4
+0×
1p
4
+1×
1+2p
4
+2×
1-4p
4
⇒
ˉ
X
=
2-9p
4
Now, -
1
3
≤p≤
1
4
⇒3≤-9p≤-
9
4
⇒-
1
4
≤2-9p≤5⇒-
1
16
≤
2-9p
4
≤5⇒-
1
16
≤X≤
5
4
.