Super Helpful Vocal Exercise
So far we have looked at all the Major Scale notes up to the 5th and bigger jumps in melody are uncommon so it makes sense to work hard on this much.
The vocal (and hand) exercise I recommend here are super effective at building your knowledge of the intervals in your ears and then translating then into simple shapes on the instrument.
On The Guitar
With a Root 6, 5, 4 or 2 there are 3 patterns that I would call, Back, Middle and Forward of the root. They're all important though I probably find the Back pattern is the least used in my own playing - it shouldn't be, but it is!
XX diagrams showing the 3 patterns XX
From Root 3 is actually a little easier under the fingers (starting on finger 1 always feels better!) so I often find myself in this shape when trying to find a melody in a hurry!
XX diagram of above XX
Singing The Intervals In Order
Start by playing each of the intervals one after another and then back down so play R 2 R 3 R 4 R 5 R 4 R 3 R 2 R as shown on Root 5:
XX diagram TAB XX
Once comfortable then sing along with your playing.
Once confident with that, try singing and playing the root anf then jumping the vocal up the interval and then checking on the guitar, again doing all the intervals in order.
This will really strengthen your ear to hear the different intervals.
When you're confident with the above you should start pushing it a bit more by playing and singing a root and then deciding a random interval and trying to sing it and then check on the guitar.
Start in one part of the neck and run al the intervals from the one root note but as you get more confident you could try moving the root note every time and singing a different interval each time - a lot more challenging and will really expose any weaknesses that you should work on.
But don't forget to have fun! :)
If you're confident with all the intervals so far, I would suggest working on this one for a week or two as a replacement for specific intervals, but continue your Play What you Hear exercise for 5 mins a day!