Android :: How To Declare Type Of Preference?

I have a preferences.xml that looks like this:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
<EditTextPreference android:name="Sample" android:enabled="true"
android:persistent="true" android:summary="Sample" android:defaultValue="3.0"
android:title="Sample" android:key="sample" /> </PreferenceScreen>

When I do sp.getString("sample", "3.0"), it works fine and returns a string, but it shouldn't be a string, it should be a float. Running sp.getFloat("sample", 3.0f) throws a ClassCastException because it is a string. What should I put in the XML so that the preference is stored as a float?