Can engagement programs be set to deliver to only a portion of the members?

Clone the program 3 times. And split the leads between the now 4 programs. But this is not a professional solution, as you don't want to maintain 4 exact clones.

I don't use emails in engagement programs directly, but programs to send the emails. If you do the same, you could alter the campaign in the program.
1. Random sample (25%) send email.
2. Wait 1 day
3. Random sample (25%) send email.
4. Wait 1 day
5. Random sample (25%) send email.
6. Wait 1 day
7. Random sample (25%) send email.
This only applies to 1 lead, so I'm not sure if it would work.

How about mixing Diederik's suggestion with the engagement program feature.

You have a smart campaign that adds leads to a stream in the engagment program and this campaign is set up similarly to what Diederik outlined above.

Smart list that identifies the leads.
Flow :
1. Add to engagement program random sample 25%  (default =Do Nothing)
2. Wait one week
3. Add to engagement program random sample 25%  (default =Do Nothing)
4. Wait one week
etc

The only thing is that as it is a random sample the leads would not be evenly split for each rep.
Of the 25%, 10% could be Rep A, 12% rep B, 3% rep C.
To achive a more even split you would have to do several smart campaigns, one for each rep's leads.

Thanks so much guys. Building on your ideas, would this work?

The engagement program has 4 streams, each stream with the same 12 emails in it. A campaign adds leads to the engagement program based on:

·         Random sample: 25% add to stream 4
·         Random sample 25% add to stream 3
·         Random sample 25% add to stream 2
·         Default add to stream 1

When the engagement program is turned on the cadence is set as:

·         Stream 1: 1 week
·         Stream 2: 2 weeks
·         Stream 3: 3 weeks
·         Stream 4: 4 weeks

After Stream 1 delivers the 1^st email, the cadence for stream 1 is changed to 4 weeks.
After Stream 2 delivers its 1^st email, the cadence for stream 2 is changed to 4 weeks.
After Stream 3 delivers its 1^st email, the cadence for stream 3 is changed to 4 weeks.

Then after that each stream should fire once every 4 weeks but always on different weeks. Does this make any sense? J

You can't change the cadence. Only to pause and normal. I would just set up all the streams to four weeks. In the campaign that adds the leads you have:

·         Random sample 25%: Wait 3 weeks + Add to stream 4
·         Random sample 25%: Wait 2 weeks + Add to stream 3
·         Random sample 25%: Wait 1 week + Add to stream 2
·         Default: Don't wait + Add to stream 1

This would make sure every week 1/4 of all leads is receiving an email. However you're not adding all leads at once. But 1 lead at a time. So it won't be evenly split 25%, 25%, 25%, 25% like Cathal mentioned.

I just set something up for a colleague in South East Asia, which might help you too. All her leads are in the default Engagement Programs with a weekly cast. But I have a batch campaign that runs every day, and leads can only go through it once per month. The batch campaign sets Marketing Suspended to False, waits 1 week, sets Marketing Suspended to True.

The effect is that leads statr the flow on a daily basis, so everything is spread out over all 30 days of the month. And the spread of the allowed week is also spread over the entire month. And the process restarts every month at the exact spread of a small group of leads. So that even better than the 25% previously workded on.

The downside of this technique is that all these leads can't be emailed for 3 out of the 4 weeks in a month. If this is a problem, you could temporary reset the Marketing Suspended in the flow of the campaign you want to run. And set it back at the end of that flow.