At temperature \( T \), the probability of ideal gas molecules with mass \( m \) having speed \( v \) is given by \( P(v) \). Two quantities \( I_1 \) and \( I_2 \) are defined in terms of \( P(v) \) as follows:
\[
I_1 = \int_0^\infty P(v) v^3 \, dv \quad \text{and} \quad I_2 = \int_0^\infty P(v) v \, dv
\]
Which of the following relationship is true?