Skype has a survey that pops up after a call called "How was the call quality?"  The frequency that users receive this survey can be changed.  

This feature is described in a number of articles:
Rate my Call in Skype for Business Server 2015
https://technet.microsoft.com/en-us/library/dn951407.aspx

Rate My Call in Skype for Business 2015

https://blogs.technet.microsoft.com/jenstr/2015/05/05/rate-my-call-in-skype-for-business-2015/

Jens Trier Rasmussen says, "The RateMyCallDisplayPercentage parameter controls how often the form is shown. You should interpret it as each X times, i.e. if the RateMyCallDisplayPercentage is set to 10 the form will be shown each 10th call."

Based on this, using the PowerShell "Set-CsClientPolicy -Identity Global -RateMyCallDisplayPercentage 1" should have increased the frequency of surveys.  This did not happen.

Based on a Microsoft Premiere Support case, for Skype for Business Online users, they should be configured to use the CPCPstnPreviewRateMyCAllClientPolicy.  That policy has RateMyCallDisplayPercentage = 100.

Clear-Host
Import-Module "C:\Program Files\Common Files\Skype for Business Online\Modules\SkypeOnlineConnector\SkypeOnlineConnector.psd1"
$CSSession = New-CsOnlineSession -OverrideAdminDomain XXXXXXXX.onmicrosoft.com
Import-PSSession $CSSession -AllowClobber
Grant-CsClientPolicy -Identity XXXXXX@XXXXXXX.com -PolicyName CPCPstnPreviewRateMyCallClientPolicy
Remove-PSSession $CSSession