Random Number not working

[QmanRocks]

I'm trying to make a random item selector (kinda like Mario Kart) and I have this in my .sk file:

on step on pressure plate:
    loop 10 times:
        set player's selected hotbar slot to slot 0 of player
        set {_number} to a random number between 1 and 4
        if {_number} is 1:
            set slot 5 of player to 1 oak plank
        if {_number} is 2:
            set slot 5 of player to 1 birch plank
        if {_number} is 3:
            set slot 5 of player to 1 acacia plank
        if {_number} is 4:
            set slot 5 of player to 1 dark oak plank
        wait a tick

But all it does is set my hotbar to the first slot. Nothing appears in slot 5 at all. I'm not sure why this isn't working, as it seems super simple.

 

[BoxMiners]

its

set {_number} to a random integer between 1 and 4