Android button background selector

I want to use the following selector for button:

<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:drawable="@drawable/jobs" android:state_pressed="true">
        <shape android:shape="rectangle">
            <corners android:radius="5dp" />
        </shape>
<scale android:scaleHeight="90%" android:scaleWidth="90%" />
    </item>
    <item android:drawable="@drawable/jobs"></item>

</selector>

But it does not work. I want to make buttons corners round and 10% small in size with the same drawable. Actually I want to give a button pressed effect using single drawable. Is it possible?